Cells

Atoms and the periodic table

Energy

Science

Y8 Science

Key Stage 3

Year 8

Y7 Science

Year 7

Y9 Science

Year 9

UNIT

Define an element and learn how different elements are represented by chemical symbols.

Elements

﻿- Hi, I'm Ms. Barrett from the Oak National Academy. Today's lesson is all about elements And this is from the atoms and the periodic table unit for Key Stage 3. Make sure you've got a periodic table with you for today's lesson, 'cause that's gonna really help you. Let's get started. So in this lesson, we are going to define an element and learn how different elements are represented by chemical symbols. So some key words for the lesson. An atom is the smallest unit of matter. You might have heard of atoms before. But don't worry if you haven't, 'cause we're gonna have a little recap in a minute. A tiny piece of matter is called a particle. And metals are substances that are usually solid, hard, shiny and good conductors of electricity and heat. So the outline for today's lesson on elements. We're gonna start with defining an element. And then we're gonna have a look at some chemical symbols. Then we're gonna have a bit of an introduction to the periodic table. And then we're gonna talk about metals and non-metals. So let's get started with defining an element. So we're gonna start with talking about atoms. As I said, you might have heard of atoms, but you might not know what they are. So atoms are the smallest unit of matter. So if we were to chop an object into the smallest pieces it could possibly be until you couldn't divide it any further, there's pieces you wouldn't even be able to see them. This would be atoms. They are the smallest unit of matter. And everything in the world is made from atoms. So whether that is the paper that you've got in front of you, a pen, the screen that you are looking at, your body, your hair. Everything is made from atoms. And this is why atoms are so, so important. In this lesson, we are going to represent atoms as circles of different sizes and colours, just like the pictures you can see here. So here we've got some particle diagrams. On the left, these are elements. On the right, these are not elements. So what do you think defines an element? What can you see the differences between these two particle diagrams? So on the left hand side, you can see that the elements are made from one type of atom. The grey solid. There's only one type of atom there. And then we've got a gas where the particles or the atoms are all black. Again, that is one type of atom. Whereas on the right hand side, we've got a liquid that is made of grey and white particles. And then we've got another solid that's made of two different types of particles or two different types of atoms. So when there is more than one type of atom, that is not an element. An element is a substance made of one type of atom. So elements can be solids. They can be liquids or gases, just like we saw on that previous slide. So remember your passcode diagrams for these three elements. So solids have fixed regular arrangement. Liquids are particles are really close together. But they haven't got a fixed or regular arrangement. And a gas, they have their atoms completely separated. Nothing is touching. So it doesn't really matter what state the element is. If there is one type of atom there, then it is an element. So a copper pipe is made from copper atoms only. If we were able to zoom in really, really, really far, all the way until we can see the atoms, which isn't actually possible. But if we could, this is what it might look like. It's solid. And you would see all the copper atoms. They look exactly the same, all lined up in that regular arrangement. And the same fill this piece of charcoal. If we zoomed on that one, you would see carbon atoms all lined up. And every single one of them would be the same. So copper and carbon are both elements. So let's check how much we understood so far. An element is a substance made of two or more types of atom. Is that true, or is that false? Have a think and also have a think about how you would justify your answer. Okay, so an element is a substance made of two type or more types of atom. Is that true? Nope, that is false. Remember, an element is a substance that is made of one type of atom, not two. It can only be an element if there is only one type of atom. Next question. Which of the following diagrams shows an element? So think carefully, what about our definition of an element? And have a think which one that applies to. Okay, do you think you've got it? The correct answer is C. That one is our element, because that's the only one that has one type of atom. A is a molecule that's got a large grey atom and two smaller black atoms. But they are different. And in B, there is a mixture of the white and black atoms. So that is also not an element. Okay, so onto your first task for the lesson. So in the first part, you are going to circle the boxes that show an element. So just like we did in that check for understanding task, have a little look, which one do you think matches the definition of an element? And then part B, complete the sentence. An element is- Fill in the rest of the definition. Pause the video here. Have a go. Come back when you're done. Okay. How did you get on? Hopefully, you didn't find that too difficult. Let's go through the answers. So the boxes that showed an element were A, D, F and G. And you can see that these are the only ones that have one type of atom. Even though A is a gas, D is a liquid, F is a gas as well, and G is a solid, that doesn't matter. They all have one type of atom present. That means they must be an element. And then of course, our definition is an element, is a substance, made from one type of atom. Right. So let's move on to our second part of the lesson. This is on chemical symbols. So each element is represented as a symbol. So here we've got the symbol for hydrogen. And hydrogen symbol is a capital H. And it's just the one letter. On the right hand side, we've got aluminium. And aluminium symbol is a with A little l. So some elements are represented by one letter. Some of them have two. But the most important thing is that first letter in the symbol is always uppercase. And if there is a second, then that one is always lowercase. So chemical symbols are used on the periodic table. You might have seen this before. This is the periodic table. And these are all the symbols of all of the 118 elements that we know. So let's see how much we've understood about chemical symbols. What you're gonna do here? There are four elements with symbols. And I want you to spot the mistake in the chemical symbol. Pause the video if you need to. Okay. So in that first one, hydrogen. What did I say the symbol for hydrogen was? Because it definitely wasn't Hyd. The symbol for hydrogen, it's actually just an H. So the important rule to remember there is chemical symbols have up to two letters. And sometimes, it's just one, depending on what element it is. So that was the mistake there. The next one, we've got magnesium. What was the mistake here? Well, magnesium symbol is Mg. But the second letter has to be lowercase. So that was the mistake on that one. The next one, nitrogen. The symbol for nitrogen is N. But remember that that first letter always has to be uppercase. And then finally, we've got potassium, and we've got capital P. And you might first look at that one and think, I can't really spot the mistake here. But if you have a look at the periodic table, and you find potassium, or you find P, you'll realise that these two don't match. And actually, the symbol for potassium is a K. So the symbol doesn't always match the name. So you might think it's potassium, it must be P. But sometimes, they're based on old names or based on Latin names, so the symbol is completely different to the name. So watch out for that one. Okay, next question. What is the symbol for beryllium? And again, if you need to pause the video and have a look at your periodic table, that's absolutely fine. All right. Did we get that one? So the symbol for beryllium is Be. So sometimes, the symbols can be quite similar. So B is actually boron, and Br is actually bromine. So they're all existing elements. But the symbols are just ever so slightly different. Next one, what is the symbol for silver? Okay, so on this one, the right answer is Ag. So that's a bit of an unusual one. S is actually sulphur, and Si is actually silicone. Even though they would seem like they should match up with silver. As I said, sometimes, you've gotta be careful that the symbols are not quite what you would expect. Right. Onto Task 2. So for this task, you're going to use your periodic table to fill in the blanks. So some of them have the symbol, but no name. And some of them have a name, but no symbol. So you need to fill them up so that everything has a symbol and a name. Pause the video here. Have a go. Best of luck. Right. How did you find that? Hopefully, you found that okay. Let's go through the answers. So the first one, we've got He. So what element did you find that was on the periodic table? That is helium. The symbol for calcium is Ca. And then we've got an O. What's that the symbol for? That was oxygen. Carbon. Carbon is a C. N. We had this one earlier. Did you remember what that one was? That one was nitrogen. Lithium. Symbol is Li. Hg. Now this is a strange one, 'cause it doesn't match the word. This was mercury. It's in the transition metals down the bottom of the periodic table. So you might have struggled to find that one. Another strange one. Lead, the symbol is Pb. Au. This is gold. Now, I bet you've come across gold quite a lot. But you probably didn't know that its chemical symbol was Au. And then finally, tin symbol is Sn. So you can see those last four are all symbols that don't really match the name, so they're ones to look out for. Really well done if you got those right. Let's move on to the next section of the lesson. So we're onto the third part now, introduction to the periodic table. So there are 118 elements in the periodic table. And this periodic table shows all the elements that we currently know. There might actually be more elements. We just haven't discovered them yet. So the elements are arranged into groups and periods. So the groups are the columns of the table. So you can see here, from 1 all the way to 0 in blue, the groups are downwards in columns. And then the periods, these are the row, so going across. So you can see here, we've got seven periods in the periodic table. And then the block in the middle, these are known as the transition metals. These have some quite complicated properties. So we don't tend to talk about transition metals too much at Key Stage 3. So if you've got your periodic table in front of you, I would suggest you write on these numbers to indicate what the periods are and what the groups are, because that will help you for the next part of the lesson. Okay. So have you got your periodic table? Let's answer some questions. Which element is in period 4 and group 2? I'll give you a few seconds to find it. So that one is calcium. Did you get that right? Well done if you did. Which element is in period 2 and group 6? Is it barium, nitrogen or oxygen? So that one is oxygen. Well done if you've got that one right. Some people sometimes get the groups in periods the wrong way round. So just make sure that you know the periods are across, and groups go down. Next one, which element is in period 3 and group 5? So that one is phosphorus. Well done if you've got those right. Let's move on to the task. So the first part of the Task 3, you're gonna complete the sentences about the periodic table. So the rows are called something. Columns are called something. And the block in the middle is called the something. Pause the video here. Have a go. Good luck. Okay, shall we go through the answers? So let's complete the sentences. Rows are called periods. Columns are called groups. And the block in the middle is called the transition metals. Give those a tick if you've got those right. Well done. Okay, let's move on to part B. So in this part, we're going to find the element. The first three questions are similar to the check for understanding task we did earlier. And the last two parts, you need to find the transition metal in periods 4 and 5. Pause the video and come back once you have completed the task. Right. Let's go through the answers. How did you get on? So the first one, period 1, group 8, you should have found that was helium. And whether you wrote the word helium or use its chemical symbol, He, either would be acceptable there. And the next one, period 3 and group 5. That one was phosphorus with a capital P for the chemical symbol. Period 5, group 7, which element was that? That was iodine. Iodine has a capital I for its chemical symbol. And in the next one, there are many options you could have had for the fourth and fifth question. So you needed to find the transition metal in period 4. So that was any element from scandium to zinc. So remember the transition metals are the block that are in the middle of the periodic table. So you could have had scandium, you could have had titanium, vanadium, chromium, anything between scandium and zinc. And the same applies to the next question for period 5. This was any element from yttrium to cadmium. So you could have had yttrium, zirconium, rhodium, palladium, anything along that period. Well done. Hopefully, you got those correct. So for our final part of the lesson, we are going to look at metals and non-metals. So you might have heard of metals before. You probably know what a metal is. But we're gonna talk through some different types. So the periodic table is divided into metals and non-metals by a stepped line. So it starts between boron and aluminium and then steps all the way down, as you can see, on the diagram. So if you've got your periodic table in front of you, I would suggest drawing this line on if it's not already there, 'cause that's gonna really help you identify which ones are metals and which ones are non-metals. So everything to the left of that step line are metals. Everything to the right of that step line are non-metals. So as you can see, there are a lot more metals on the periodic table than there are non-metals. So how would you group these elements into metals and non metals? So we've got gold. We've got oxygen. We've got carbon which is charcoal. And we've got a silver ring. So which ones do you think are metals, and which ones do you think are non-metals? So the metals are gold and silver. These are two quite common metals. A lot of jewellery is made out of gold and silver. So you might have heard about these or come across them. And then on the right hand side, we've got the non-metal. So carbon, this version of carbon is a black solid. And then oxygen is a gas. So inside that gas canister will be a gas. And it's usually in the air. We can't see it. And that is not a metal. Okay. So using your periodic table, you're going to work out if the krypton is a non-metal. Is that true, or is that false? And then make sure you justify your answer. Okay, so that one was true. Krypton is a gas. And it's found on the right hand side of the periodic table. It's part of group 0 which are called the noble gases. So it's definitely not a metal. Okay. So let's move on to Task 4. So what you're gonna do in the first part is you're gonna sort the elements into the correct columns in the table. So I've got eight elements here. And you just need to have a look at your periodic table and decide which ones are metals and which ones are non metals. Pause the video here. Have a go. And I'll see you once you're done. Okay. Hope you got on okay with that. Let's go through the answers. So the metals were caesium, magnesium, cobalt and thallium. So that must mean the non-metals were neon, arsenic, chlorine and sulphur. Give those a tick if you've got those right. And if you've got any the wrong way round, make sure that you have put them back into the right columns. Okay. Let's move on to part B. So use your periodic table to find the element name and chemical symbol that matches the statement. So the non-metal in period 7. The metal beginning with a V. The non-metal in group 3. The metal in group 7. And the metal in group 2 and period 3. So again, use your periodic table to find these. And make sure that you've got that metal and non-metal step line written on your periodic table, 'cause you're gonna need that to help you with this task. Pause the video. Good luck. Okay. Let's go through the answers. So the non-metal in period 7, there is only one non-metal in period 7, and that was oganesson. So that chemical symbol is Og. The metal beginning with V. Well, this one is in the transition metal block. and this is vanadium. And that chemical symbol is a V. So that was a little bit of a clue there. The non-metal in group 3. So remember the groups go downwards. And the only non-metal is boron. That chemical symbol is a B. The metal in group 7. So group 7 is mostly non-metals. But there is one metal right at the bottom, and that is tennessine. And that chemical symbol is Ts. And the metal in group 2 and period 3 was magnesium with the chemical symbol Mg. Really well done for making it through all of those tasks. That was our last task for the lesson. You've done a fantastic job on the first lesson of this unit. So let's summarise everything that we have learned today. An element is a substance made from one type of atom. A chemical symbol is a one or two letter representation for an element. The periodic table is arranged into periods and groups. Elements with similar properties are in the same group. The periodic table can be split into metals and non-metals. And that is the end of the lesson. Have a go at the exit quiz and see how much you've learnt. Well, I hope you enjoyed today's lesson, and you've got loads of new chemistry knowledge. Well done for completing all the tasks. You've done really, really well. Thank you for using the Oak National Academy. And I'll see you next time.

Define a compound, write compound formulae and name compounds based on the atoms they contain.

Compounds

Understand the difference between physical and chemical changes and write equations using word and symbol equations.

Chemical reactions

Describe what is meant by 'conservation of mass' and apply this to chemical and physical changes.

Conservation of mass

Understand that elements have different properties and how the periodic table has been developed over time according to our knowledge of these properties.

Development of the Periodic Table

﻿- Hi folks. My name's Mrs. Farrow. For today's session you're gonna use a pen and a piece of paper so it's a good idea to put your mobile devices on silent or switch them off to help to avoid any distractions. If you need to take a moment to sort that, then please do so now and press play when you're ready to resume. Today's lesson is about the development of the periodic table. We want to have a look at how the elements have been arranged, taking a look at some of the different properties the elements have and how the periodic table has changed over time as our knowledge of these properties and the particles that make up the elements have changed. Some of the key words that you might spot as we go through today's session include: Properties, these the characteristics of a substance. They're used to describe and identify substances and it has been used to sort the elements into the correct groups within the periodic table. The periodic table, this is an arrangement of all of the elements based on their atomic number and properties and an element, an element is a substance made from just one type of atom. We've broken today's lesson about the development of the periodic table down into three cycles today. First, looking at what are properties? Second, focusing on the early periodic table and how it changed over time. And then lastly, the modern periodic table. So if you're ready, we'll get started and take a look at what are properties. Well properties is a phrase that we use to describe the characteristics of a substance. Properties tend to fall into one of two groups. Substances either can show chemical properties or physical properties. Chemical properties include things like reactivity, so if an element reacts with water or oxygen, for example. We also have flammability. Flammability is similar to reactivity in that burning is a chemical reaction. The ease with which something catches fire is described as its flammability. Acidity, that describes whether the substance is behaving like an acid or an alkaline in reactions, and toxicity describes whether it is poisonous to living things. Physical properties that we might use to describe a substance are things like the colour. Density, this is the mass per given volume. If something has a lot of mass in a set volume, then it's going to be dense and more likely to sink in water. If something has very little mass per given volume, then it's going to be less dense and more likely to float on water. We can also describe a substance's hardness, so if is strong or brittle and we can look at the melting and boiling points. These are the temperatures at which physical changes take place. Melting being changing from a solid to a liquid, and boiling when a substance changes from liquid to gas. So let's do a quick knowledge check. Which the following is a physical property of substances? Is it A acidity, B density, or C flammability? The correct answer is B density. The other two listed here are chemical properties. Which two of the following are chemical properties of substances? You can choose from A toxicity, B hardness, C acidity and D colour. The correct answers are A toxicity and C acidity, toxicity describing how it affects living creatures and whether it is poisonous or not, and the acidity describing whether it behaves as an acid or alkaline within chemical reactions. Now it's time for you to have a go at a practise task. We would like you to define the term property and then reading through the list, circle the chemical properties and underline the physical ones. You'll need to give yourself a little bit of time to complete this task and give it your full attention. So we suggest you pause the video now and press play when you're ready to hear the correct responses. How did you find it? Let's take a look at how you got on. So the first task asks you to define the term property. Now you don't have to have word for word exactly what I've written but your answer should follow the same general themes. Property is the physical or chemical characteristics of a substance, allows us to describe and identify it. Part B asks you to circle the chemical properties and underline the physical ones. So let's take a look. Reactivity, this is how the substance reacts with either oxygen or water or other elements. And so this is a chemical property. Colour is a description of the physical appearance and so should be underlined as a physical property. Flammability, a description of how readily something catches fire which is a chemical reaction and so should be circled. Hardness, how likely something is to break or how strong it is, is a description of its physical qualities, and so should be underlined. Acidity describes whether it behaves as an acid or alkaline within chemical reactions and so is a chemical property that should be circled. And lastly, we have melting point. Melting is the physical change from a solid to a liquid and so this should be underlined as a physical property. Well done if you've got all of those right. If not, don't worry, you can always go back and have a look at this first section of the video again. So we've taken a look at what are properties and properties are important as they played a key role in the ordering of the elements in the early periodic tables. So let's take a look at who and how the elements were ordered in the beginning and how it has developed over time to become the periodic table that we know and secretly love today. So the first scientist to contribute to ordering the elements within the periodic table was somebody called John Newlands in 1863. Newlands spotted a pattern. He found that if he wrote the elements in order of atomic weight that each of the eighth elements had very similar chemical properties and behaved in similar ways when he reacted them with oxygen and water. He referred to this as his Law of Octaves, and we can see here from the image, that Newland's work enabled the early formation of some of the groups that we see today. Li for lithium, Na for sodium, and K for potassium, all being in the same column because they had very similar properties. This forms Group 1 of the modern periodic table today. The third column within Newland's table also has beryllium Be, magnesium Mg and calcium Ca. This forms Group 2 of the modern periodic table today or the beginning of it anyway because they all show similar chemical properties during reactions. So Newlands' work was incredibly useful at identifying the different properties the substances had and grouping them together. His work was relatively closely followed by that of a Russian scientist named Dmitri Mendeleev. Dmitri Mendeleev arranged the elements by their atomic weight in the same way that Newlands did. However, making him slightly unpopular, he decided that some of the atomic weights had been calculated wrong by his fellow scientists and figured that he could move those around in order to maintain groups of elements with similar properties together. To then add insult to injury, he left gaps within his table for elements that he believed had been undiscovered, suggesting that his fellow scientists needed to do more work. Whilst having been ridiculed quite significantly during his life for his table, it turns out that once it had been published, many of the elements that he'd left gaps for were later discovered. In fact, some of the elements were even discovered after his death and so his true genius wasn't recognised until long after he had created his table. The undiscovered elements are shown here within his table by hyphens. You can also see that he has the groups across the top and the beginning of what looked like periods down the side of the table. It was quite some time then, before anybody else took the periodic table and began to make changes. It was in 1913 a scientist called Henry Moseley was working as part of a scientific group who discovered the proton. In doing so, he was able to reorder Mendeleev's table and instead of using the atomic weight, he started to use the atomic number, the number of protons found within the nucleus of each of the elements. This led to the modern periodic table as we know it today, with the eight groups as we can see identified across the top, and the six periods. By having this slightly stepped appearance, showing it stepping down between Group 2 and the transition metals and then up again before reaching Group 3, allowed elements with similar properties to still be kept together. The periodic table hasn't changed much since Moseley's time, aside from the addition of Group 0. Time for a quick knowledge check. Which scientist proposed the Law of Octaves? Was it A Newlands, B Mendeleev, or C Moseley? Octaves refers to eight and it was John Newlands who spotted that every eighth element showed similar properties. Which two of these scientists ordered their tables based on the atomic weight? A Newlands, B Mendeleev, or C Moseley. The correct answer is A Newlands and B Mendeleev. Both of these two scientists used atomic weight, whereas Moseley used the atomic number. Which scientist left gaps in their table for the undiscovered elements? Was it A Newlands, B Mendeleev or C Moseley? The correct answer is B Mendeleev, although he wasn't thought of favourably for doing so. And finally, which scientist discovered the proton which helped to create the modern periodic table? A Newlands, B Mendeleev or C Moseley? The correct answer is C Moseley. Well done if you've managed to get all of those right. Now it's time for a practise task. In task A, we'd like you to match the scientists to their periodic table ideas and in B, starting with the earliest, number the scientists to show the order in which they contributed to the development of the periodic table. I'd recommend that you pause the video now and give this task your full attention and when you're ready to hear the answers, press play. How did you find that? Hopefully not too tricky. Let's see how you've done. So Newlands should be matched with saw each eighth element had similar properties. Mendeleev, quite cleverly, left gaps for undiscovered elements and Moseley ordered the elements by their atomic number. We then asked you to start with the earliest, number the scientists to show the order in which they contributed to the development of the periodic table. It was John Newlands who first spotted that each eighth element had similar properties and so he should be numbered one. This was then followed up by Dmitri Mendeleev and then finally, after the discovery of the proton, the periodic table was reordered by Moseley. Well done if you've got all of those correct. If not, you can always go back and watch this section of the video again and have another go. So we've taken a look at what are properties and how the early periodic table was largely ordered using them. Now it's time to have a look at the modern periodic table and compare it to some of the earlier versions. So the modern periodic table arranges their elements of who said by the atomic number. Remember, this is the number of protons that we find in the nucleus of each of the atoms. The metals are on the left of the periodic table and the non-metals on the right, as you can see here. On the left hand side of the line, going from aluminium stepping down, those are all metals. You can see there are considerably more metals in the periodic table than there are non-metals. The columns are numbered as Groups from one to seven and then Group 0 on the end. Each of the rows is now what we refer to as a period and gives us additional information about the structure of the atoms that we find in those rows. It's quite common to be asked to compare Mendeleev's periodic table with that of the modern version. If we take a look at the two, we can see that there are some significant similarities. We can see that there are groups in both the modern and Mendeleev's table and that there are clearly rows. We can identify that some of the elements are occurring in the same places, although there are also some important differences and that's what we're going to try to spot now. One of the first major differences is that Mendeleev's table was arranged by the atomic mass, whereas the modern period table is arranged by atomic number. Mendeleev couldn't possibly have used atomic number because the proton hadn't been discovered when he put his table together. Mendeleev's table left gaps. Although this made him unpopular with fellow scientists, it actually turned out to be a work of genius as later, those elements were discovered and placed in and so in our modern periodic table, there are now no longer gaps. Mendeleev's table, due to the lack of discovery of some elements, had only 63 elements, whereas our modern periodic table as close to 118. And then lastly, you may notice if you look closely, that Mendeleev's table has no Group 0, whereas this does exist on the modern periodic table today. This is because Group 0 are known as the noble gases. This group of gases are what's called inert and unreactive. They were the last elements to be discovered because they are so unreactive, they weren't happened upon by accident during experiments by scientists and so were added much later as a group on the end, on their own. Let's do a quick knowledge check there and see what you can recall. True or false? Mendeleev's periodic table is exactly the same as the modern periodic table. Being as we've just had a little go at spot the difference, I'm going to say that this is false. Mendeleev's table was arranged by the atomic weight, whereas our current periodic table is arranged by atomic number. So, over to you for a practise task. The first part of this task asks you to place a tick in the correct boxes to show if the description applies to either Mendeleev's periodic table or the modern periodic table. You'll want to pause video now so that you can take some time to consider your answers and when you're ready to hear the correct responses, press play. How did you do? Great, I'm sure. Let's take a look and see if your answers match up with mine. So the first description says it's arranged by atomic number. The atomic number is the number of protons and so must refer to the modern periodic table. The Group 0 elements being missing is a feature of Mendeleev's periodic table. Gaps were present for the undiscovered elements and so this must also be Mendeleev's table, as all elements we now believe to have been discovered and placed within the gaps that were left and finally arranged by atomic weight. Well, the modern periodic table as we've already said, was arranged by atomic number, so arranged by atomic weight must be a feature of Mendeleev's table. Well done if you've got all of those right. Let's take a look at task B. Task B asks you to complete the sentences by filling in the gaps. This will give you a nice summary paragraph about the development of the periodic table. You'll need to take a little bit of time to consider your responses, so we suggest you pause the video now and press play when you're ready to go through the answers. Let's take a look at how you got on. It was John Newlands who proposed the Law of Octaves as he spotted that every eighth element had similar properties. Dmitri Mendeleev helped to create the modern periodic table by leaving gaps for the undiscovered elements. Both Newlands and Mendeleev ordered the elements by their atomic weight. The modern periodic table is arranged by the atomic number and it has columns, that we call groups, and rows, that we refer to as periods. Well done if you got those right. On to our third and final task. Whose table of elements improved on Newlands' and how? There's three marks available for this question, so we need to be very clear in answering it. We need to identify which scientist improved on Newlands' table and how that was an improvement. You'll want to pause the video and take a few moments to consider your response, making sure that you explain your answer clearly, highlighting how the table was improved upon. When you're ready to hear the answers, press play. How have you done? Right, so three parts. We must be able to achieve at least one mark for saying who the scientist that followed Newlands was, Mendeleev. So if you've written Mendeleev you've achieved one of the marks available out of the three. We then need to go on to explain how his table improved. Well, he left gaps for the undiscovered elements. What this meant was that the elements with similar properties were kept in the same groups and so led to the development of the groups that we see today within the modern periodic table. Really well done. That was a tricky one. So if you've managed to get marks on this question, you're doing really well. We've reached the end of our lesson today. So let's take a look at some of our key learning points. Properties are the chemical and physical characteristics of substances. The three major contributors to the periodic table were Newlands, Mendeleev and Moseley. The layout of the periodic table has changed as we've learnt more about the properties and particles that make up the elements. And the modern periodic table is arranged by the atomic number. This is the number of protons. It has columns called groups and rows called periods. I hope you've enjoyed our lesson today as much as I have. I'd like to suggest that you have a go at the exit quiz before you sign out today. Thank you for choosing to use Oak National Academy and we hope to see you again soon. Bye for now.

Describe the common properties of metals and non-metals and how different uses relate to their properties.

Metals and non-metals

﻿- Hi, folks, my name is Mrs. Farrow. For today's session, you're going to need a pen and a piece of paper, and it's a good idea to switch off or silence any mobile devices to help avoid distractions. If you'd like to take a few minutes to sort those things out, press Play when you are ready to resume. So today's session is going to be about metals and non-metals. We're going to describe some of the common properties of both metals and non-metals and how we use different materials based on their properties for different uses. So let's move on and take a look. Some of the keywords that you will encounter during today's lesson include malleable, these are substances that can be bent or hammered into shape without breaking, a conductor, which is a material that lets heat or electrical energy pass through it, and materials that are hard but can break easily are referred to as being brittle. We've broken today's session down into four sections. Those are, what are properties, properties of metals, the properties of non-metals, and then some of the uses of metals and non-metals. So if you're ready, we'll jump straight in and take a look at what are properties. Well, a property is a characteristic of a substance. It's how we describe how it looks, behaves and reacts. Some common properties that we often talk about of different substances include things like melting point. Really important that we're careful here with our language. Lots of students when asked to say what melting point is will say, "Well, it's the point at which something melts." You're entirely not wrong, it is, but we're not adding any value, we're not actually adding a scientific explanation to what the phrase means, so we need to be careful that we are using the phrase, the temperature at which a solid changes to a liquid, okay? So a melting point is the temperature at which a solid changes to a liquid. We then have boiling point, again, the same issues is often seen here. We should be saying that it is the temperature at which a liquid changes to a gas, so we're being really specific about what state change is occurring and the idea that it is at the temperature that that is occurring. And then finally, conductor. So if something is a conductor, it's a material that is going to allow electrical or heat energy to pass through it, this being the opposite of insulators, which you may have looked at, which don't allow either heat or electricity to pass through them. So, some important keywords there regarding properties which relate to our metals and non-metals that we're going to look at moving forward. So let's do a little quick knowledge check and see what you can recall. So we've got True or False. The melting point is the temperature at which a solid changes to a gas, True or False? Hmm, okay, so this is tricky because the melting point is a temperature, so the first little bit of that sentence is correct, but then it says, at which a solid changes to a gas. Well, when something's melting, it's changing from a solid to a liquid, so we should have said that this statement is false. Our reasoning for that is, melting is the process of changing from solid to liquid, not solid to gas. Well done if you've got that one right. Now it's time for you to have a go at a practise task. You'll want to pause the video now in order to complete this task to the best of your ability. We're asking you to draw lines to match up the keywords to the correct definition. Press Pause, and when you're ready to hear the correct answers, you can restart the video. So let's take a look and see how you got on. Melting point. Now we talked about this in some detail. The melting point should be matched to the temperature at which a substance changes from a solid to a liquid. We've then got boiling point. This is the temperature at which a substance changes from a liquid to a gas. And then finally, conductor. This should be matched with a material that allows heat and electrical energy to pass through it. Well done if you've got all of those right. It's really important to practise our key terms and definitions as it enhances your science writing to use these phrases as much as possible. Right, so now we've taken a look at properties, it's time for us to apply our learning and look at some properties of metals. Properties of metals include being solid at room temperature. They tend to be very strong, this makes them incredibly useful as building materials. They're conductors of both heat and electricity and so are useful in terms of, in the kitchen, when we are looking at making saucepans or baking trays, and conduct electricity, we use them in our wires and electrical devices often. They tend to have a high density. This means that they have a large mass per given volume. That's quite a tricky idea to get our heads around, but what it ultimately means is that they're likely to sink when placed in water. They are shiny and reflect light and so look pretty when making things like jewellery, and they tend to have very high melting and boiling points. This means we need to get them really hot in order to change their state. So being solids at room temperature, we need to get them very hot in order to melt them to liquids, and even hotter again in the hope of getting them to change to a gas. Now metals have some unique properties which make them very useful to us as well. They are malleable. Now malleable means that can be bent and hammered into shape without breaking. I'm sure many of you have had the odd paperclip and sat and bent and fiddled with them, and you'll notice that you can twist them into many different shapes without the paperclip from breaking, and this is because it is a malleable material. Metals are useful because we can hammer them into lots and lots of different shapes and therefore use them for a variety of different things. Metals are sonorous. This means that they make a ring or ping sound when struck. This is why numerous musical instruments are made of metal. If you think about the cymbals as part of a drum kit, they make a lovely tinking noise when hit with the drumstick. A gong made out of plastic would be no good. It would make a dull thud as opposed to that lovely crashing noise. And then finally they are ductile, which means that they can be drawn into wires. This is particularly useful, being as we know that they can conduct electricity. The layers in the metal allow the atoms to slide over one another, and this is what allows them to be drawn out so very thin in order to make the small electrical wiring that we need in components such as our mobile phones and laptops. Let's do a quick knowledge check then. What do we call the property of a substance that can be bent or hammered into shape without breaking? Is it, A, sonorous, B, malleable, C, brittle, or D, dense? The correct answer is B, malleable. What does sonorous mean? Is it, A, it can be drawn into wires, B, it makes a ringing sound when struck, C, can be bent and shaped without breaking, or D, melts at low temperatures? The correct answer is B, it makes a ringing sound when struck. Well done if you were able to get that one right. What do we call the property that means a substance can be drawn into wires? Is it A, sonorous, B, malleable, C, brittle, or D, ductile? The answer to this question is D, ductile. The metal is able to be drawn into wires as the atoms are in layers and slide over each other. Now it's time for a practise task. We'd like you to pause the video and spend some time defining, writing the meaning, of the following key terms, sonorous, malleable, ductile. When you're ready to hear the answers, press Play. Shall we take a look at how you got on? Now you don't have to have written these word for word the same as mine, but it does need to follow the same general scene. Sonorous, then. What does sonorous mean? Well, it's a description of a material that makes a ringing sound when struck. Remember those cymbals? Malleable. Malleable is a material that can be bent or hammered into shape without breaking. And then lastly, ductile. A material that can be drawn into wires. These are all important properties of metals only, and this is what makes them particularly useful for certain roles that we require them to do, which we're gonna take a look at later. We've had a look at properties and the properties of metals, now it's time to jump into the properties of non-metals. The properties of non-metals include, they tend to be liquids or gases at room temperature. They are brittle, this means that they break easily if they are solids. Things that are brittle tend to be quite crumbly. They are poor conductors of heat and electricity, often referred to as insulators. We often use them around our electrical wires in order to insulate electricity, and most of our clothes are insulators too. They have a low density. This means they have a small number of particles per given volume and so will often float in water. They are dull and do not reflect light easily. They are not ductile and so cannot be drawn out thinly into wires. And they have low melting and boiling points, so only slight heating is enough to often change them from solids into liquids or gases. Let's do a quick knowledge check then. Non-metals are poor conductors of electricity. True or False? The correct answer to this question is True. Non-metals do not allow electricity to pass through them and so they are considered poor conductors. Good job if you've got that one right. Next question, select the two properties of non-metals, so we're going to pick two of the following list. A, brittle, B, shiny, C, low melting points, and D, high density. The correct answers are, A, brittle, and C, low melting points. Now it's time for a practise task. The first part of this task asks you to delete one of the options in the brackets so the sentences read correctly. You'll need to pause the video now and give this task your full concentration and effort, and when you think you're ready to hear the answers, press Play to resume. How did you find it? Let's see how you got on. Sentence number one, non-metals cannot usually conduct electricity. Sentence two, non-metals have a low density. Sentence three, non-metals are poor conductors of heat energy. Sentence four, non-metals are brittle. And sentence number five, non-metals have low melting and boiling points. Give yourself a tick for each question. How many did you get right out of five? Lots of them, I'm sure. Don't worry if you've struggled with any aspects of this though, you can always go back and watch this section again if you need to. Task B asks you to put a tick in the correct box to show if the property belongs to a metal or a non-metal. Again, it's a good idea to pause the video and give this task your full attention and a bit of time. When you're ready to hear the answers, press Play and we'll go through them together. Let's see what you've got right then. So the property, malleable, this belongs to metals. Something which has a low melting and boiling point easily changes from solid to liquid to gas. This must be a property of non-metals. The substance which conducts heat. I know this one from personal experience having burnt myself on metal spoons I've left in saucepans before. This is a metal. Brittle means it can easily be broken. As metals are malleable, this must apply to non-metals. And finally we have shiny, which is a property of metals. Well done if you've got all of those right. Where are we on our journey? Well, we've taken a look at properties, the properties of metals and the properties of non-metals. Now it's time to dive in and taken a look at some of the uses of metals and non-metals and how they link to the properties we've already seen. So objects are made from different materials. The materials are selected based on their properties. So, for example, we use metals to make electrical cables because they have the properties of being a conductor of electricity and ductile. It will be no good trying to use a non-ductile, brittle insulator in order to make electrical cabling. Non-metals are used to make things like insulation that we find in our cavity walls and our lofts. This is because they are poor conductors of heat energy and so much more effective at keeping our homes warm. Filling our roofs and cavity walls with metal would be a mistake, as they would easily conduct the warmth out of our homes. Let's take a look at an everyday object like a frying pan. If we take a look at the base of the frying pan, you can see it's made of metal. Metals are good conductors of heat and have very high melting points. These are important properties, because we don't want our frying pan base to melt when we put it on a high heat, but we do need it to allow the heat to pass through in order for the food that's inside it to cook. The handle, on the other hand, is often made of a non-metal, like a plastic, because non-metals are poor conductors of heat. This means the handle stays cooler and safer to hold. You may have saucepans at home which have metal handles and you'll have to be very careful when picking them up, perhaps using a cloth in order to avoid burning your hand. Why don't we make the whole frying pan out of non-metals? This is an easy one to answer. Can you imagine if your frying pan was made out of something like plastic? You're going to get an awful sticky mess on the hob when trying to fry an egg. Let's do a quick knowledge check and see what we can recall. True or False. Metals are used in electrical cables because they are sonorous. True or False? These true or false questions are tricky. Part of this statement again is correct, metals are used in electrical cables. They are. However, it then says because they are sonorous. Now remember, that's one of our key terms, which means it makes a ringing noise when struck, so the answer to this question is, False. Metals are used in electrical cables because they conduct electricity and they are ductile, not because they are sonorous. Now it's time for a practise task. You'll need to pause the video to give you these tasks your full attention. The first one asks you to look at the image and complete the sentence and answer the question regarding the kettle. When you're ready to hear the answers, please press Play. Let's see how you've done. The first task asks us to complete the sentence. The jug is made from metal, because it is a good conductor of heat. Then we're asked to explain why the handle is made of plastic. Plastic is a non-metal. It is a poor conductor of heat energy, or you could say insulator. A person can touch the handle and it will not be too hot. Well done if you got those right. Remember, when we're answering in longer sentences, you don't have to have it written word for word the same, but you should have the same ideas within your sentences. Let's take a look at the next task. Draw lines to match the use with the property. We have church bells, power cables, saucepan, and jewellery. You need to select the most appropriate property from the list opposite to join it up with. High melting points, sonorous, shiny, and conducts electricity. Pause the video and have a go, and then we'll take a look together at the answers. When you're ready, press Play. How'd you get on? Let's have a look. Well, church bells need to be able to ring out to call people to service and in celebration, so they need to be sonorous. Power cables need to allow electricity to pass through them in order to charge our devices, and so they need to be able to conduct electricity. A saucepan is going to be placed on the heat and so should have a high melting point, and jewellery needs to be shiny. Well done if you've got all of those correct. So we've reached the end of our session together today. Let's take a look at some of our key learning points. Materials are chosen to make different objects based on their properties. Metals and non-metals have different properties. Metals' properties include being shiny. Malleable, meaning they can be bent and hammered into different shapes. Strong and sonorous, making a ringing noise when struck. Non-metal properties include having low melting and boiling points, and so don't require much heating to melt them or turn them into gases. They are poor conductors or insulators and they tend to be very brittle. Before signing off, why not have a go at our exit quiz? Well done, and thank you for all your hard work today, I really hope you've enjoyed this lesson. We'd like to take this opportunity to thank you for using Oak National Academy and we hope to see you soon. Bye for now.

Describe the physical and chemical properties of Group 1 metals and trends in their reactions with oxygen and water.

Group 1

﻿- Hi, guys. My name's Mrs. Farrow. For today session you're going to need a pen and a piece of paper. And it's a good idea to put your devices on silent or switch them off to try and help avoid any distractions. If you'd like to get those things sorted by pausing the video now and press play when you're ready to resume. Today we're going to be looking at Group 1, this is one of my favourite groups in the periodic table. We're gonna describe the physical and chemical properties of the Group 1 metals and the trends that we see in their reactions with both oxygen and water. So we're in for some pretty exciting stuff today. Some of the keywords that you're gonna come across during today's session that you can keep an eye out for include, combustion, is the process of burning. We've got oxidised, or oxidation. This is when an element combines with oxygen. And density, a measure of the amount of matter or mass in a particular volume. Okay. Today's session has been broken down into three distinct parts. We have cycle one, "What is Group 1?" Number two, "Physical properties and trends". And then lastly, the "Chemical properties and trends". So let's jump in and take a look at "What is Group 1?" Well Group 1 metals react with water to form alkali compounds. So Group 1 is what we refer to as being the alkali metals. These are found in the first group or column of the periodic table as shown here in the image and they consist of lithium, sodium, potassium, rubidium, caesium, and francium. They are all quite exciting, and I'm very excited to talk to you about them today. What kind of properties are we looking at? Well, properties can be either physical or chemical characteristics of a substance. Physical properties, we're talking about physical properties, we talk about their density, the amount of material per volume. This usually is an indication of whether it's going to float or sink in water. The appearance, so what colour does it have? Is it shiny or is it dull? And the melting and boiling point, what temperature do you have to get it to in order to change its physical state? And then some of the chemical properties, we can look at the reactivity with other elements or water. We can talk about the acidity, be that whether it has acid or alkaline properties, and it's toxicity. So is it harmful to living substances? Let's do a quick knowledge check then. True or false? The alkali metals are found in the first row of the periodic table. Okay. So the answer to this one is in fact false. The alkali metals are found in Group 1, which is the first column, not row. If you're not sure about columns and rows you need to have a look at our periodic table video. Okay, next one. Which of the following is not an alkali metal? We've got A, magnesium. B, lithium. C, sodium and D, potassium. The correct answer is A, magnesium. It's actually an alkali earth metal found in Group 2 of the periodic table, not Group 1. So now it's over to you for a practise task. There are two parts to this task. The first part is asked, why are the elements in Group 1 known as the alkali metals? And in the second part we would like you to colour the part of the periodic table which shows the location of the alkali metals. You'll need a little bit of time to do this so if you'd like to pause the video and press play when you're ready to hear the correct answers. Let's take a look at how you got on. This first question doesn't need to be word for word the same as mine, but it should follow the general theme that the Group 1 metals are called alkali metals because they react with water to form alkali compounds. Well done if you have something along those lines. Part B asks you to colour the correct column to show the location of the alkali metals in the periodic table. And you should have coloured this section here, indicated on the diagram, which includes lithium, Li. Sodium, Na. Potassium, K. Rubidium, Rb. Caesium Cs and Francium Fr. Good job if you managed to get those all correct. Well done. Tasks will get trickier as we go through. That's what Group 1 are and where they're found. Now let's start looking at some of their physical properties and the trends that we see. The Group 1 metals have some typical properties of metals including them being good conductors of heat. They are shiny and they are good conductors of electricity. Now these are all properties we would expect them to have as metals, and are common to other metals that we see in the periodic table. However, they do also have some quite unique physical properties which make them rather different to what we would normally expect from a metal. Firstly, they're soft and can be easily cut with a knife. They tend to have much lower densities than other metals and some will even float on water. And they have low melting and boiling points and so don't have to be got particularly warm in order to change from solid to liquid or liquid to gas. If we take a look at the melting and boiling points of the alkali metals, you can see that they decrease as you go down the group. Lithium has a melting point of 181, so in order to get it to change from a solid to a liquid we need to heat it to 181 degrees. We can see this number decreasing steadily as we go down the group through sodium, potassium and rubidium, all the way to caesium at 28 degrees C. So in theory, cesium would melt in the palm of your hand, that's if it didn't explode first of course. We see a similar trend in boiling point, starting off much higher and gradually decreasing as you go down the group. Now let's take a look at density. The alkali metals generally become more dense as you go down the group. Although unfortunately as you can see from the table the pattern isn't quite perfect as potassium is slightly less dense than sodium. Water has a density of one gramme per decimeter cubed. And those elements which have a density less than one are going to float. And those alkali metals with a density greater than one will sink. Looking at the data in the table, can you predict which ones would float and which ones would sink? Let's take a look. Lithium, sodium and potassium all have a density lower than that of water and so will float. Whereas rubidium and caesium have a density of higher than one gramme per decimeter cubed, and so will sink when put into water. Let's do a quick knowledge check. Elements in Group 1, are all metals with high density, true or false? The answer to this question is false. Group 1 metals have low densities generally, and some of them even float on water. Next question. What happens to the melting points and boiling points of the Group 1 elements as you go down the group? Do they A, both increase. B, they both decrease or C, the boiling points increase but the melting points decrease. The correct answer is they both decrease. It becomes easier to change the Group 1 metals from solids to liquids and liquids to gases, as you go down the group. Now it's time for you to have a practise task on your own. We would like you to complete the sentence by using one of the words below and then answer the questions which follow. You're going to need to give this task your full attention and spend a little bit of time doing it. So we suggest you pause the video now and press play when you are ready to see the correct answers. Right, let's see how you got on. So task A says "Complete the sentence using the words below. The boiling points of the alkali metals are something than the boiling points of other metals." And you had a choice of higher, lower, or the same as. Let's take a look. Boiling points of the alkali metals are lower than the boiling points of other metals, is that correct sentence. Task B, "How do the melting points of the alkali metals compare to other metals?" Well here you could have used the sentence above to help you with the structure. Only this time instead of boiling points, we're looking at melting. So, the alkali metals have much lower melting points than other metals. And question C asked you to "Describe the trend in melting points as you move down the Group 1 metals." As you go down the Group 1 metals, the melting point decreases. Well done if you've got all of those right. If not, don't worry, you can always go back and re-watch this section of the lesson again. So we've had a look at some of the physical properties and trends, now it's onto the really exciting part. The chemical reactions of the Group 1 metals and the trends that we see as we go down the group. Let's take a look at the reactions with oxygen. The reaction between an alkali metal and oxygen is called oxidation, because oxygen is reacting with the alkali metal. A general word equation would look something like this. An alkaline metal plus oxygen gives an alkali metal oxide. All of the reactions of the alkali metals with oxygen follow this same pattern. Let's give you an example of a real reaction. Lithium, an alkali metal, reacts with oxygen to form lithium oxide. It's important to realise that we can also represent this reaction as a symbol equation, although at this point you're not expected to be able to use them. It's worthwhile getting familiar with some of the symbols that are commonly used. So for this reaction it would be Li plus O 2 gives Li 2 O. Let's have a little practise at this, shall we? Here's our general word equation for reference. Alkali metal plus oxygen are our reactants and so found on the left hand side of the arrow. The alkali metal oxide is our product and so found on the right. Let's take a look at another example together. In this example we're going to look at sodium reacting with oxygen. When sodium reacts with oxygen the alkali metal oxide formed is sodium oxide, and this is our product. It's your turn to have a go. I'd like you to write the word equations to the reactions of potassium, rubidium, and caesium with oxygen. This is going to take you a little time and you'll need to think carefully about it. So pause the video and press play when you're ready to check your answers. Okay, time to see how you got on. Let's have a look. So potassium and oxygen react to form potassium oxide, rubidium and oxygen react to form rubidium oxide, and caesium and oxygen react to form caesium oxide. Now let's have a look at the trends that we see when each of these metals react with oxygen. When the alkali metals are cut, they do appear shiny at first, but they quickly become dull and white. This is due to the reactions with oxygen from the air. We actually keep the alkali metals under oil in order to prevent this from happening, and to stop them from getting wet. Which you'll understand why we do later on in today's lesson. This changing of colour due to the reaction with oxygen is known as tarnishing. Lithium tarnishes quite slowly, sodium more quickly and potassium the fastest. And so we can see the reaction getting much faster as we go down the group. When we heat the alkali metals in oxygen, they will actually combust or burn and a chemical reaction begins to take place. Lithium burns the least vigorously with a pretty red flame. Sodium burns slightly more vigorously giving an orangey flame. And potassium, my favourite, burns most vigorously with a lilac flame. Now let's take a look at the reactions of the alkali metals with water. We know that they react with water to form alkali compounds because we said that this is where their name comes from. The general word equation is that an alkali metal will react with water to form an alkali metal hydroxide plus hydrogen. If we look at an example, we can take lithium, for instance, lithium will react with water to form lithium hydroxide plus hydrogen gas. We know it's hydrogen gas 'cause if collected it makes a squeaky pop sound. Again, we can show these reactions as a symbol equation. You're not expected to be able to write these yet yourself but we'll take a look anyway. Lithium, Li, plus water, two lots of H2O, react to give two lots of lithium hydroxide 2LiOH plus H2, which is hydrogen gas. Let's have a little more practise at these equations and see how you can get on. Here's our general equation. The alkali metal reacts with water to form an alkali metal hydroxide and hydrogen gas. We have the reactants again on the left hand side and the products on the right. Let's take an example of sodium again. Sodium reacts with water to form sodium hydroxide and hydrogen. What I'd like you to do, is have a go at writing the word equations for the reactions of potassium, rubidium, and caesium again, but this time with water. You'll need to pause the video now and to come press play when you're ready to check your answers. Let's see how you got on with these equations then. The first one is potassium plus water reacts to form potassium hydroxide and hydrogen. The three that we've looked at, so far, lithium, sodium and potassium are possibly examples that you may have seen in school. Next was caesium, it's rubidium, sorry. Rubidium reacts with water to form rubidium hydroxide and hydrogen. And lastly, we have cesium and water, which react to form caesium hydroxide and hydrogen. Well done if you got all of those right. Hopefully starting to begin spot the pattern and how to answer these, complete these equations. Let's see what trend we see then as these Group 1 metals react with water. Lithium is the least reactive at the top of Group 1. When it's added to water it fizzes and moves slowly around the water's surface giving off bubbles of hydrogen gas. It's quite exciting, but by far not the best one. Then we have sodium. Sodium is much more reactive. When added to water it melts and it whizzes quickly across the surface of the water. If you're lucky, the hydrogen produced will catch fire and it produces an orangey coloured flame. And then lastly, by far my favourite and the most dramatic that we're allowed to do in school, is potassium. This is the most reactive and it will melt and move across the surface of the water incredibly quickly, whizzing around producing hydrogen, which often ignites and gives a lilac flame. Unfortunately, due health and safety, we're not allowed to show caesium or rubidium in school. It would be far too dangerous. But there are lots of clips that you can see online. Let's do a quick knowledge check to see how much you can recall. The first three elements of Group 1 are lithium, sodium and potassium, but which one is the most reactive? The correct answer is potassium. It's the lowest down the group and therefore the most reactive. Next question. Which gas is produced when the Group 1 elements react with water? This one will really test to see how well you've been listening. Is it A, carbon dioxide. B, hydrogen, or C, oxygen? The correct answer is B, hydrogen. Well done to all of you who got that. Now it's time for you to have a little practise task. In this first part of the practise task we'd like you to complete the sentences by filling in the gaps. When you think you've completed it to the very best of your ability, press play and we'll go through the answers together. Ready to take a look and see how you got on? So, sentence one. The Group 1 metals are called the alkali metals. They have low densities and melting points. Lithium is the least reactive in the group. They react with water to give off hydrogen and make an alkali solution. Good job on getting those right. Now for the second part of your task. I'd like you to answer the two questions. The first one asking you to describe the trend in reactivity of the alkali metals as you go down the group. And the next part, asking you to complete the word equations for the reaction of sodium with oxygen and potassium with water. Again, pause the video now and take your time over these and press play when you're ready to hear the answer. Okay, let's see how you got on. First part then, "Describe the trend in reactivity of the alkali metals as you go down the group." As you go down the Group 1 metals from lithium towards caesium, they become more reactive with both water and oxygen. Well done if you have something like that. Doesn't have to be word for word but you will need to make sure it has those general points. And then task C, asks you to complete the word equations. We've helped you a bit here by putting in spaces for you to write the answers. So sodium reacts with oxygen to form sodium oxide. Okay. Notice the changing is the ending of oxygen in order to show it's now part of a compound. Then we have potassium reacts with water to form potassium hydroxide and that gas that's been given off, hydrogen. Well done if you manage to get those correct. If you need to go back and watch any parts of the lesson again, you can do at any point. So let's take a look at what we've learned today. The Group 1 metals are also known as the alkali metals. The alkali metals have some unique properties. They have unusually low melting and boiling points. They have very low densities and are soft. They are very reactive with oxygen and water and the metals become more reactive as you go down the group. I hope you've enjoyed our lesson today as much as I have. We'd like to thank you for using Oak National Academy and we hope to see you again soon. Bye for now.

Describe the trends in reactivity of Group 7 elements and how they react with different Group 7 elements and elements from other groups.

Unit Overview: Atoms and the periodic table

Lessons: