This quiz will test you on your understanding of group 1 metals, and will also contain some revision questions linked to previous lessons in this topic.

Revision: True or false - When a non-metal reacts, it forms a positive ion.

Revision: What kind of mixture is distillation used to separate?

Revision: How many ELEMENTS are shown in the image?

What name is given to group 1 elements?

What gas is produced when an alkali metal reacts with water?

Describe the density of group 1 metals.

The general word equation for the reaction between water and alkali metals is:

As you go down group 1, the reactivity....

Group 1 elements

﻿Hi, my name is Dr.Patel, and welcome to today's lesson in this topic of Atomic Structure and Periodic Table. In today's lesson, we're going to be learning all about Group 7 elements. Before we get started, I'd like you to do the couple of things for me. Please make sure that you're sitting in a nice, quiet space that's free of any distractions. So, if that means that you need to close down any of those computer tabs, do so now. Great. The next thing I'd like you to do is make sure that you've got today's date and title written at the top of your page, and today's title is Group 7 elements. So in today's lesson, you're definitely going to need the equipment that's listed on the screen, and you're especially going to need a copy of your periodic table. If you haven't already done so, please go and download this from the downloadable resource section and then we'll carry on with the lesson. So, this is the periodic table that you should have in front of you. We're going to be looking at group 7 elements. So, if you find the column which has got fluorine, chlorine bromine, iodine, astatine and tennessine, then, that's the column we're going to be looking at today. So in today's lesson, we're specifically going to look at the physical properties of group 7 elements. In the following two lessons, we're also going to look at the reactive properties of group 7 elements. But for today, we're just going to focus on the physical properties. So hopefully, by the end of today's lesson, you should be able to describe the main physical properties of group 7 elements. And hopefully, you should be able to explain them using particle model. So, to start today's lesson, we're going to start with a warm up quiz. Pause the video now and have a go at answering these three questions which are based on knowledge from a previous lesson. So, here's what you should have got. Make sure that you really know these facts so that you know that negative ions are formed when non-metals gain electrons. It's also really important that you understand the difference between a chemical change and a physical change. And, these are the three examples that you'll need to know about in terms of physical properties. Pause the video now and make any corrections that you need to, resume playing the video once you've done this. Okay, so we're going to start off by looking at the physical properties of group 7 elements. Now, group 7 elements are also known as the halogens. What are they known as? Exactly. They're the halogens. Say that again? Good, the halogens. Okay? So, let's look at the physical properties of group 7 elements. Can you list any of those physical properties that we might be looking at? Good. And another? Good. And the third? Good. So, well done if you said density, melting point, and boiling point. Those are the three that we're going to be looking at with respect to group 7 elements. So before we go into the melting point, the boiling point, and the density of group 7 elements, let's look at some other general physical properties of these elements. So on the screen, you can see an image of chlorine, bromine, and iodine. And one thing that is really striking about the three is that they are very different colours. And that's probably one of the first key features of group 7 elements. And, you do need to know the specific colours of each one of those halogens. So, chlorine is normally a pale green colour, bromine is normally an orangey brown colour, and iodine is normally a purply brown colour. Now, you do need to remember these colours as they will come in important when we're looking at reactions of group 7 elements. The next thing that you need to obviously know is that they are not metals. So, which side of the periodic table are non-metals found on? Excellent. They're on the right hand side of the periodic table. So, if you look on the right hand side of the periodic table, that's where group 7 is. Now, one really important difference between metals and non-metals, there are other exceptions of course, is that they don't conduct electricity. So, halogens are key examples of elements that actually don't conduct electricity. Now, what do you notice about the solid that's there? Well, it looks quite crumbly, doesn't it? And that's because as a solid, iodine is actually very, very brittle. Do you know what the word brittle means? It just smashes apart very, very easily. And then, the final thing that you need to know is that each one of these is actually quite poisonous in its own way. And they're very, very pungent in the way that they smell. Pause the video now and see if you can remember what the properties, the general physical properties that I've talked to you about. So, these are what should have thought about. How many did you get correct? Good. Now, if you've left any of them out, then please do add them to your notes because they're quite important physical properties that you need to know about. Now, let's look at trends in melting points. So, have a look at the table and just try and work out, are the numbers in melting point increasing or decreasing as you go down the group? So, what do you think? Okay, so the numbers are going from more negative to more positive. And therefore, the numbers are increasing. Now, we're going to have a go at trying to describe the trend in melting point. And, you need a slightly more detailed answer than the numbers are increasing. So, a really good description includes a general description of the trend which we've already just gone over; so, there's an increase in the melting point. But, you also need to include two other sections. So, you need to state values from the table, and you need to use comparative language. So, more examples of comparative language have we come across already? Good. Whereas, however, in comparison to, lower, higher, more, less, lowest, and highest. They're all examples of words that you can use to compare two numbers. So, I'm going to put an answer on the screen and I want you to pause the video and see if you can identify each one of these three sections in my answer. And then after this, after we've looked at melting point, you're going to have a go at writing your own answer, so make sure that you really understand where these different points are in my answer. Pause the video if you need some time to read this. Okay. So, you'll notice that I've represented my general description using green. And then, I've included specific values from the table, and I haven't listed lots and lots of values. I've just taken two points that illustrate best what I'm trying to say. And because I'm trying to say that melting point is increasing, I've chosen to take the lowest number and the highest number, and compare just those two numbers. And then, the last thing I've used is comparative language. So, you'll notice that I used the word, whereas, and I've used the word lowest and highest. I haven't used the word low and high because just saying something is low, that isn't necessarily comparing it to something else. You have to say lower or lowest or more or less, okay? So, make sure that you understand this and then you're going to have it go in a minute. Okay. So now, I want you to pause the video and have a go at answering this question. So, you need to describe the trend in boiling point as you go down group one. There's a couple of sentence starters to support you. Make sure that you include the three main points that you need in a really good answer. Pause the video now and have a go. Okay. So, here's what you should have got. Pause the video now and compare your answer with the one in front of you. If you've used slightly different numbers, that's fine. But you wouldn't have been able to use the word lowest and the highest, because they wouldn't be the lowest and the highest. So, you would have to use the comparative words, lower and higher. Pause the video now and compare your answer with the one on the screen. So, explaining physical properties. Now, it's great that you feel more confident with being able to describe physical properties and the trends as you go down, but let's look at why that boiling point increases. So, look at the diagram of fluorine, chlorine, bromine, and iodine. What do you notice? There's two main things that you should notice from those diagrams. So, well done if the first thing you noticed was that they're in pairs. Do you remember what we call it when we've got two atoms that exist in a pair and they're exactly the same? Good. Diatomic. So, well remembered if you said diatomic. Now, so, all group 7 elements are diatomic molecule. And, that just means that there are two of the same type of atom joined together. Now, what's the other thing that you notice as you go down the group? Exactly. They're getting bigger. The atoms within each diatomic molecule are getting bigger. Now, that's a really important reason for why the boiling point increases. And, let's explain that in a little bit more detail. Now, while I'm explaining why the boiling point increases as you go down the group, I want you to just put your pens down and make sure that you're fully paying attention. Good. So, what do you notice about the arrangement of diatomic molecules as you go down the group? So, fluorine is at the top of group 7, and iodine is at the bottom of group 7. What do you notice about the arrangement of the diatomic molecules? What's happening? Good. So, you can see that the diatomic molecules in fluorine are much further apart than in iodine. And actually in iodine, all the diatomic molecules are touching each other. What does that resemble in iodine? What state of matter does that resemble? So, when I say state of matter, I mean, solid, liquid, or gas. Excellent. So, it resembles a solid. So, remember a solid, all the particles are touching each other and they're arranged in a very ordered arrangement. Now, if iodine is a solid, what does that make fluorine? Good. Fluorine is a gas. And you can see that because the diatomic molecules are really far apart. Now, what about chlorine and bromine? Let's go for bromine 'cause that's probably the clearest. Good. It represents a liquid. So, you can see that the diatomic molecules are touching each other, but it's not as ordered as the arrangement that you see in iodine, and there's small spaces in between those bromine molecules. So, bromine is a liquid. Fluorine is a gas, chlorine is actually a gas, bromine is a liquid, and iodine is a solid. Now, why is it that that happens? And which of these do you think has the highest boiling point? So, which one will boil at the highest temperature? So, well done if you said iodine. Now, if it's a solid at room temperature, it means that it's got a very, very high boiling point; otherwise, it wouldn't be a solid. Which one has got a lower boiling point? Good if you said fluorine. So, fluorine must have a lower boiling point because it's already a gas at room temperature. Let's try and explain that in terms of the particles. Now, the reason that fluorine is a gas at room temperature is because there is a really weak force of attraction between those diatomic molecules. So, you can see from the diagram, they're quite far apart and they're far apart because the force of attraction between them is very, very weak. How do you think the forces of attraction in iodine compare? So, well done if you said that they are stronger forces of attraction. The forces between the diatomic molecules must be stronger because otherwise, they wouldn't be touching. Now, let's imagine when I'm trying to boil something, what I'm trying to do is I'm trying to pull apart those diatomic molecules. So, each pair of yellow circles, I'm trying to pull away from the other pair of yellow circles in fluorine, and in iodine, each pair of purple circles, I'm trying to pull away from the other pair of purple circles. I'm trying to pull away the diatomic molecule from the next diatomic molecule. So, which one is going to take more energy to pull apart? The one that's got stronger forces of attraction, or the ones that have got weaker forces of attraction? Which ones will take more energy to pull apart? Exactly. So, if you said iodine, iodine takes much more energy to pull those diatomic molecules apart compared to fluorine. And so, the reason that iodine has got a really high boiling point is because it takes a lot of energy to break those strong attractions between the molecules. Now, we know that's something tricky to get your head ground, so, if you want to pause the video now and take some notes and just make sure that you understand this before we do a quick quiz, do that now. Okay. So, let's see how much you understand and how much you remember. So, group 7 elements are called alkaline metals. True or false? So, that is false. They are actually called what? Well remembered. Halogens. So, group 7 are known as the halogens. What happens to boiling point as you go down group 7? So, does it increase or decrease? Do you remember? Good! It increases. So remember, we said that iodine is a solid at room temperature, and that's because it's got a much higher boiling point, and a much higher melting point actually. What happens to the melting point as you go down group 7? So, think back. Iodine is a solid at room temperature. Good. It increases. So, iodine melts at much higher temperature than the other group 7 elements. So, as you go down group 7, do the forces of attraction between molecules get stronger or weaker? Good. They get stronger. So, you can actually see that in iodine, all the diatomic molecules are touching each other; and that's because there's a really strong force of attraction between the diatomic molecules. Whereas if you look at fluorine, there's a really weak force of attraction between those fluorine diatomic molecules; and that's because those forces of attraction are much weaker. So, as you go down group 7, does it take more energy or less energy to break those forces of attraction? Good. It takes more energy to break those forces of attraction. If you look at iodine, they're much closer together because there is a stronger force of attraction. And think about it. If you're holding onto something really, really strongly, it's going to be much harder for someone else to come and pull you apart from it. So, for this question, you may want to pause the video just to give you a bit more reading time. Have a read through the question and see if you can work out whether this is true or false. Now, did you get false as your answer? Well done if you weren't fooled. Now, the reason that iodine has got a higher melting and boiling point is because actually, the forces of attraction between the iodine diatomic molecules are very, very strong. And so, that's why this is false because actually instead of weak forces of attraction, it needed to have been strong forces of attraction. Okay. So, you may need to do the same with this one. Pause the video, have a read, and decide whether it's true or false. So, well done if you said that this was true. Fluorine does have a lower melting point and a lower boiling point; and that explains why it's a gas at room temperature. And that's because there are very weak forces of attraction between the diatomic molecules, so you can see that the fluorine diatomic molecules are quite far apart from each other. And that's because there is a very weak force of attraction between them. And therefore, it takes very little energy to break these. And at room temperature, there is enough energy to actually break these so that they'll fall apart. Now, it's really important to note that it's not the atoms and the bonds between the atoms that breaks. It's the forces of attraction between the diatomic molecules, okay? So, be very careful about what you're saying is breaking. It's the force of attraction between the molecules. Okay. So now, it's time for an independent task. Now, be really careful when you're answering these questions because describe means say what you see, so describe the trend. So, remember back to when we were describing trends; that's what it's asking you for. And for question four, the command word is explained. So, you need to say why, and you need to use the forces of attraction and the arrangement of the particles in order to explain. So, you can use a support tool that is also on the screen in pink. Pause the video now and have a go. Okay. So, here's what you should have got for questions one, two, and three. And here's what you should have got for question four. It's really important that you didn't say atoms. So, the forces of attraction are not between the atoms, they're between the diatomic molecules. So actually, if you wrote the word diatomic molecule, that's even better, and they get stronger. And, it takes more energy to break the forces of attraction between those diatomic molecules. Pause the video now if you need to make any corrections and then resume playing the video once you've done this. So, that brings us to the end of today's lesson. Hopefully, you're a little bit more familiar with describing the physical properties of group 7 elements, and that you can explain these properties by using forces of attraction between the molecules. Please make sure that you go and complete the quiz at the end of this lesson to really test just how well you understand it, and to celebrate all your hard work in today's lesson.

This quiz will test you on your understanding of group 7 elements, and will also contain some revision questions linked to previous lessons in this topic.

Revision: How many ATOMS of OXYGEN are shown in the image?

Revision: What gas is produced when an alkali metal reacts with water?

Revision: What is the charge of any ion from group 7?

Revision: When a group 7 element reacts, it wants to:

What name is given to group 7 elements?

Describe the colour of bromine.

Describe the trend in melting and boiling points as you go down group 7.

Iodine has the highest melting point because...

Group 7 elements

Describe trends in physical properties of group 7 elements

Explain the trend in physical properties of group 7 elements

In this lesson, we will describe and explain the trends in the physical properties of group 7 elements.

Combined Science

Y10 Combined Science (Higher)

Key Stage 4

Year 10

Group 7

Atomic structure and periodic table (HT)

UNIT

Atoms, elements and compounds

Chemical formulae and conservation of mass

Mixtures, filtration and crystallisation

Separation by distillation

Separation by chromatography

Atomic structure

Development of the atomic model

Isotopes

Isotopes case study lesson

Electron Configuration and the Periodic Table

Periodic Table development

Why elements react

Group 1

Group 7 Displacement

Comparing the reactivities of Group 1 and 7 elements

Displacement reactions: Ionic equations

Review (Part 1)

Review (Part 2)

When a liquid EVAPORATES, what happens to the MOVEMENT of the particles?

When a liquid CONDENSES, what happens to the ARRANGEMENT of the particles?

Revision: Name the process by which a gas will turn into a liquid.

A student separates a mixture of dyes using chromatography. How many dyes are in the mixture shown in the diagram?

A student separates a mixture of dyes using chromatography. Which dyes are in the mixture shown in the diagram?

In which part of the atom are protons and neutrons found?

What is the CHARGE of a proton

What is the CHARGE of an electron?

What is the mass of a neutron?

What does the atomic number represent?

What does the atomic mass represent?

Lithium has an atomic mass of 7 and an atomic number of 3. How many protons are there in lithium?

Lithium has an atomic mass of 7 and an atomic number of 3. How many electrons are there in lithium?

Lithium has an atomic mass of 7 and an atomic number of 3. How many neutrons are there in lithium?

Revision: What is an element?

How many electrons are there in a magnesium atom? You will need to use your periodic table to answer this question.

What is the electron configuration of magnesium? You will need to use your periodic table to answer this question.

What group is sodium in? You will need to use your periodic table to answer this question.

How many electrons does chlorine have in its outer shell? You will need to use your periodic table to answer this question.

What are the columns called on the periodic table?

What does the group number represent?

In the early periodic table, what was used to arrange the elements?

Revision: What is the name given to group 0 elements?

Revision: Why are group 0 elements so unreactive?

Revision: Describe how the  boiling and melting point of group 7 elements changes as you go down the group?

Filtration is used to...

Revision: What physical property is used to separate a mixture of two liquids during distillation?

Who discovered the plum pudding model?

Which scientist discovered the neutron?

Which statement best describes the arrangement of electrons in plum pudding model?

Which one of the following scientists was involved in developing the nuclear model?

What happens to the boiling point of noble gases as you go down the group?

Describe the reactivity of group 7 elements as you go down the group.

What is an isotope?

Calculate the relative atomic mass for copper. Give your answer to 3 significant figures

Lesson overview:Group 7

Atomic structure and periodic table (HT):