Lesson video

- Hello, I'm Miss Barrett from the Oak National Academy.

Today's lesson is all about atomic structure and this is part of the atomic structure and periodic table unit in Key Stage four.

Make sure you've got a periodic table with you today, 'cause that's gonna be really helpful when we are drawing some atoms. Let's get started.

So in today's lesson, we are going to describe the structure of an atom in terms of the number of protons, neutrons, and electrons.

Understand atomic mass and atomic number and use them to calculate the number of subatomic particles.

So you may have come across the atomic structure in Key Stage three, but we're gonna have a little refresh today.

So here are some key words that you might recognise, from Key Stage three that are gonna help us in today's lesson.

An element is a substance made from one type of atom.

The periodic table shows all known elements and is arranged into periods and groups.

An atom is the smallest unit of matter.

So what are we gonna do today? Well firstly we are going to look at the structure of an atom, and then in the second half of the lesson we are going to look at atomic symbols.

Let's get started with structure of an atom.

So atoms can be represented in different ways and if you google the word "atom," you'll have all different pictures come up that are all slightly different.

This is the model that we are going to use in today's lesson and we're going to learn how this structure works.

So everything in the world is made from atoms. So whether that is the chair that you are sat on, the table that you might be lent on, everything in the world is made from atoms. And the atomic structure that we know today is the result of many, many years of research.

The structure was really difficult to figure out because the atom is absolutely tiny.

And in fact, if you look at my picture on the right hand side, the radius of the atom, so from the nucleus to the outside of the outer shell, on average is one times 10 to the minus 10 metres.

So that is 0.

0000000001 metres.

So that is absolutely tiny.

We cannot see them with our naked eyes.

We can't even see them with the microscopes that you might have seen or used in school.

It took hundreds of years to actually figure out what the structure of the atom looks like.

But now we've got a pretty good idea and that's what we're gonna talk about today.

So atoms are made from three subatomic particles.

These are protons, neutrons, and electrons.

So my diagram here, the protons are the red circles that have the plus written in them and the neutrons are green circles that don't have any charge written inside and the electrons are around the outside of the atom and they are purple with the minus.

So every element has a different combination of protons, neutrons, and electrons, and that's what makes different elements unique.

So firstly we're gonna talk about the nucleus.

The nucleus is the centre of the atom and the nucleus contains protons and protons are positively charged.

So remember protons, positive.

We give them a relative charge of plus one and neutrons are neutral, which gives us a charge of zero.

So both protons and neutrons are in the nucleus, and this is where the mass of the atom is, because both protons and neutrons have a relative mass of plus one.

This means they are equal to each other in mass, and the mass of the atom is concentrated in the centre of the atom in the nucleus.

So what do you think the overall charge of the nucleus is? That's right, it's positive.

Now if we think about it, we've got protons which are positively charged and then neutrons which have no charge.

So overall the nucleus has to have a positive charge.

So now we'll look at the electrons.

Electrons orbit the nucleus in shells, sometimes known as energy levels, and these are at fixed distances from the nucleus, which is the centre of the atom.

They have a negligible mass and in fact that is one over 2,000.

So a very, very, very small number.

And we can say it basically weighs almost nothing and they are negatively charged.

So they have a relative charge of minus one.

So they are opposite to protons, but equally opposite.

You may come across the term, valence electrons.

And these are just another term for outer electrons, and these are the actual electrons that take part in chemical reactions.

So you can see my diagram on the right hand side here.

We've got the nucleus in the middle, we've got three shells shown here, and then we've got electrons that are studied throughout those shells.

And in fact, electrons fill the shells in a very particular pattern.

The first shell fits up to two electrons, the second shell fits up to eight, and the third shell fits also up to eight electrons.

Beyond this point, it gets a lot more complicated, but we're not going to do that at Key Stage four.

So what's in-between the shells and nucleus? Nothing! The rest of the atom is empty space.

All of the mass is in the centre of the atom and electrons are orbiting around the outside.

But nothing, there is nothing else.

Everything else is just empty space.

Right, so let's check how much you've understood so far.

Which two subatomic particles have a charge? Remember you've got to select two.

Did you get it? So the two subtopic particles that have charge are electrons and protons.

Do you remember what charge they've got? So electrons have a negative charge.

Protons have a positive charge.

Neutrons don't have a charge.

Which two subatomic particles have mass? So the two subatomic particles that have mass are the neutrons and the protons.

And remember that is in the centre of the atom in the nucleus.

Which subatomic particles orbit the nucleus in shells? So there's only one correct option here and that is electrons.

Electrons are the ones that orbit the nucleus in those shells, also known as energy levels.

Which two subatomic particles are found in the nucleus? So it had to be the two locations that we've not talked about yet.

That is the neutrons and protons.

Remember subatomic particles in are either in shells or the nucleus.

True or false, the whole atom has mass? Don't forget to justify your answer.

So for that one, that is false because most of the atom is empty space.

We have subatomic particles in the nucleus, subatomic particles in the electrons in the shells and the rest of the atom is just empty.

Okay, final question before we're gonna move on to the task.

What is the radius of an atom? Is it one times 10 to the minus one metres? Is it one times 10 to the minus 10 metres or is it one times 10 to the 10 metres? Okay, so remember atoms are absolutely tiny, we can't see them.

So the only option that makes sense there, is one times 10 to the minus 10, one times 10 to the minus one is 0.

1 metres.

So that would be something that we could be, that would be visible with our eyes.

And one times 10 to the 10 is an absolutely massive number.

So that atom would be huge.

So that is not correct.

Okay, so we'll move on to the first task of the lesson.

In the first part, you're going to complete the table with the charge mass and location of each subatomic particle.

And then there's two questions to answer below.

Good luck, pause the video and I'll see you when you get back.

Hello again.

How did you get on? Let's go through the answers.

So the charge for an electron is.

minus one, the charge for the neutron is zero, they don't have any charge.

And the charge for the proton is.

plus one.

Did you get those right? Well done if you did.

What about mass then? So electrons, they have essentially a mass of zero or you can say one over 2,000, but a very, very small number.

Neutrons plus one and protons also plus one.

So neutrons and protons are have an equal mass.

What about the location? Where are electrons? Well electrons, they're in the shells.

Neutrons are in the nucleus and protons are also in the nucleus.

Really good job if you've got those right.

Okay, what is the overall charge of the atom? Now think very carefully about all the charges that we've got.

What would the overall charge be? That's right, it would be neutral or zero because the electrons have a negative charge, but the protons have a positive charge and they are equally and oppositely charged.

So that means they cancel out and therefore the atom is neutral.

And what about the nucleus? If we just think about what's in the nucleus, what's the charge? Well that would be positive because the only thing that has charged in the nucleus is the protons.

Neutrons are neutral, so therefore the nucleus must be positive overall.

Really well done.

Let's move on to the next part.

So now you're gonna have a go at a six mark question.

I want you to treat this as if it's an exam question.

So think very carefully about what you're going to write in your answer.

So you are going to describe the structure of an atom with reference to all subatomic particles, relative masses and charges.

Six mark questions should on average take six minutes, but try your best, see how you get on and come back once you have finished, good luck.

Okay, so that was a little bit of a challenge, but hopefully you didn't find it too difficult.

So I'm gonna show you six things that should have been included in your answer.

If you've written this as four sentences and you've written it like a mini essay, that is absolutely fine.

Just look out for the points that are in the mark scheme.

The atom is made of protons, neutrons, and electrons.

So if you've mentioned those subatomic particles at any point you get that first mark.

Protons have positive charge, neutrons have neutral charge.

Electrons have negative charge.

The protons and neutrons are in the nucleus.

The electrons are in the shells which are round the outside of the atom.

The rest of the atom is empty space.

Now I imagine that might be the mark that you might miss 'cause people always forget to mention that the rest of the atom is empty space.

But that is really, really important to think about.

So if you also did an annotated diagram, that would also be acceptable because that would also show all of those points in picture form.

So you would still get the marks.

So give yourself a mark out of six, see how much you've mentioned out of those six things.

And if you've got any marks, then give yourself a massive pat on the back because six mark questions in science can be pretty tricky.

So well done.

Let's move on to the next part of the lesson.

So in the second half of the lesson we're going to look at atomic symbols.

So what's this? This is the periodic table.

So hopefully you've seen this before.

You might have come across this at Key Stage three.

And if you look closely at the periodic table, you'll see all of the atomic symbols for the different elements.

And you'll see that each atomic symbol has two numbers on it.

So for example, if we have a look at oxygen, there's a 16 and 8 written on there.

So what do those numbers mean? So here is the atomic symbol for oxygen again, and the first thing that you'll recognise is the chemical symbol.

So for oxygen it is an O and the bigger number is atomic mass.

So 16 is oxygen's atomic mass, and that is the number of protons and neutrons added together.

The smaller number is known as the atomic number.

And the atomic number tells us the number of protons that that element has and that also happens to be equal to the number of electrons in the atom because each atom has an equal number of protons and electrons.

So how do you think we calculate the number of neutrons? Well, to calculate the number of neutrons, we need to look at the mass number because this is made of protons and neutrons.

And remember, we know what the number of protons is from the atomic number.

So to calculate the number of neutrons we need to subtract the protons away from the mass number.

So for oxygen, the mass number is 16 and the proton number, well that is the atomic number and that is 8.

So we do 16, subtract 8, and that gives us 8 neutrons.

So in this case, the number of neutrons, protons, and electrons are all the same.

They're not always but for oxygen, every single one of the subatomic particles, there are eight of them.

So be really, really careful because some periodic tables have the numbers the other way around, they might have the mass number on the bottom and the atomic number on the top.

So try not to think of it as bottom number and top number.

Just think about the mass number always being the biggest number on the periodic table.

And that makes sense because the mass number is protons and neutrons and the atomic number is just protons.

So we're gonna calculate the subatomic particles in helium this time.

So here's helium's atomic symbol and the number of protons.

Can you remember how we work that out? Well that is the atomic number.

So that is 2.

Helium has 2 protons.

And now we're gonna think about the electrons.

Remember that the number of electrons is always equal to the number of protons.

So that is also 2.

And now we're gonna think about neutrons and we've gotta do a little calculation here.

So we have to do the mass number, take away the atomic number.

That gives us also 2.

Well done if you got that right.

So on the right hand side you'll see the structure of the helium atom.

We've got the two protons and two neutrons in the middle, in the nucleus, and then the two electrons orbiting around the outside in a shell.

So what do you notice about the atomic numbers going across the periodic table? Have a little look on this diagram.

What's happening to those atomic numbers? As you can see, the atomic numbers are increasing by one as you go across the period.

So hydrogen is number 1, helium is 2, lithium is 3, beryllium is 4, et cetera.

So the proton number is what defines which element an atom is.

So what's the overall charge of the atom? We mentioned this earlier.

Protons are plus 1.

Electrons are minus 1.

So the overall charge must be zero.

So remember the overall charge of an atom has to be zero.

So if you accidentally work out that your electrons and protons are a different number and not equal, then you've made a mistake somewhere.

So go back and check it.

Okay, so we're gonna do an "I Do, We Do." I'm gonna model how we do this and then we're going to have a go at the next one together.

We're gonna calculate the number of subatomic particles in boron.

So the protons, we look here at the atomic number.

The protons is 5.

Electrons are equal to protons, so that's easy.

That is also 5.

And then neutrons, here we do mass number minus the atomic number.

So the number of neutrons and protons added together, take away just the protons.

That gives us 6 neutrons for boron.

And as you can see in this one, the subatomic particles aren't all equal.

The neutrons, there's one more neutron than there is protons and electrons.

Okay, let's do the next one together.

Calculate the number of subatomic particles in fluorine.

So protons, what do you think this one is? That's right, the protons, there are 9.

What about electrons? Yep, the electrons are also 9.

And the neutrons, we need to do a quick calculation.

We do 19 minus 9.

That gives us 10 neutrons.

Really well done if you've got that right.

I think it's time to check how much you've understood so far.

So what is the atomic number of hydrogen? Have a look at your periodic table if you need to.

Have you got it? The atomic number of hydrogen is 1.

So remember that means hydrogen has one proton.

What is the atomic number of magnesium? Have a little look on your periodic table.

Magnesium's atomic number is 12.

What is the atomic mass of hydrogen? So the atomic mass of hydrogen is also 1.

So its proton number is 1, and its atomic mass is also 1.

We're gonna think about what that means in a second.

What is the atomic mass of magnesium? Magnesium's atomic mass is 24.

Now how many neutrons does hydrogen have? Its mass number was 1 and its atomic number was 1.

What do you think? So hydrogen has zero neutrons.

It's the only element in the periodic table that doesn't have any neutrons.

How many neutrons does magnesium have? Magnesium has 12.

12 neutrons.

Okay, next question.

Deduce the number of protons for each element.

We've got boron, carbon, and nitrogen.

Have a look on your periodic table and figure out what the number of protons is.

Pause the video if you need to.

Okay, so boron has 5 protons.

Its atomic number is 5.

Carbon has 6 and nitrogen has 7.

So remember this is equal to their atomic number, and you should have found that boron, carbon and nitrogen are all next to each other in a line on the same period of the periodic table.

Deduce the number of electrons for each element.

I'm not gonna give you as long on this one because this should be pretty straightforward.

So the number of electrons for each element is 5, 6 and 7.

So remember, the electrons are always equal to the protons in an atom.

Deduce the number of neutrons for each element.

I'll give you a bit longer on this one as you're gonna have to do a quick calculation.

Okay, have you got all three? So boron has 6 neutrons, carbon also has 6 neutrons and nitrogen has 7.

So you'll notice here that boron and carbon have the same.

So the protons, they are always different in every single element, but neutrons aren't necessarily.

Really well done.

Let's move on to the task.

So in the first part of the task, you are going to complete the sentences.

Have a little read through, pause the video and come back once you're finished.

See you then.

Okay, how did you get on? Shall we go through the answers? So the number of protons is the.

atomic number.

The number of electrons is.

equal to the number of protons, the number of neutrons is the.

mass number minus the atomic number.

Really well done if you've got those right.

So part B of this task, I've given you four different elements and some of them have missing atomic numbers and atomic masses and in the box below you are going to fill in the blank boxes.

So tell me how many protons or electrons or neutrons that particular thing has.

Okay, good luck, pause the video, come back once you're finished.

Okay, so let's see how we got on.

So for the first one, we've got Mg, that was magnesium.

And the top number or the bigger number for magnesium was 24.

So what does that mean its atomic number is? It's got 12 protons, electrons, and neutrons.

So that must mean magnesium has a atomic number of 12.

So we've got titanium here and you've got the mass number and atomic number.

So this time you need to calculate the protons, electrons and neutrons.

It's got 22 protons, that's the atomic number, therefore it also has 22 electrons, and then to calculate the number of neutrons, mass number minus atomic number, 26.

Here we've got Na, this is sodium, we've got a missing atomic number.

So we also have the number of neutrons, but we don't actually have the number of protons.

We're gonna have to do a bit of a calculation.

Remember the mass number is equal to the protons and neutrons.

So if we do 23, take 12, that gives us an atomic number of 11, which is the proton number.

And remember, electrons are always equal to protons.

So that is also 11.

So for the last one, we've got argon and I've given you the atomic number.

So remember what that means in terms of protons, that means it's got 18 protons and I've given you the neutrons, which is 22.

So if we add these two together, that will give us the mass number.

The mass number is 40 and protons was 18, and the electrons are equal to the protons, so that is also 18.

Give that a big tick if you've got that right and a big pat on the back.

Well done.

So in part C of this task, we have six different elements and you need to find the chemical symbol, the protons, the neutrons, and the electrons.

You're gonna need your periodic table for this part.

So pause the video, have a go, and I'll see you once you're done.

Okay, how did we get on? So let's go through the answers.

So the symbol for teryllium was Te, and its atomic number is 52, so that means it's got 52 protons.

The electrons are always equal to the protons, so it also has 52 electrons.

And the neutrons, we needed to do a bit of a calculation.

Its mass number was 128.

So we minus the protons, 52 and that gives us 76 neutrons.

So iron, the symbol is Fe, it's got 26 protons, 26 electrons, and 30 neutrons.

Bismuth, the symbol is Bi and it's got 83 protons, 83 electrons, and 126 neutrons.

Caesium is Cs and it's got 55 protons, 55 electrons, and 78 neutrons.

Strontium is Sr and it's got 38 protons, 38 electrons and 50 neutrons.

And then finally lead, the symbol is Pb and it has 82 protons, 82 electrons, and 125 neutrons.

Well done.

That was quite a complicated task, so good job.

So for the final part of Task 2, I've given you four different clues and you need to work out what the name of the element and the symbol of the element it is that it's describing, and then that's gonna give you an anagram for the symbols.

And you need to unscramble the chemical symbol anagram, and that's gonna spell out another element.

Use your periodic table if you need to.

Pause the video, have a go and I will see you when you're finished.

Right let's go through the answers.

Do you think you've managed to get the element from the anagram? Let's find out.

Something that has 7 neutrons.

This is nitrogen.

So you've had to look at the mass numbers and atomic numbers to figure out that nitrogen is the only one that has 7 neutrons.

Its atomic number and mass number add up to 24.

This is oxygen, it has a mass number of 16 and an atomic number of 8.

That adds up to 24.

Neutrons and protons add up to 85.

That was rubidium and something that has 20 protons.

Well, this is just gonna be the number 20 on the periodic table and that is calcium.

So we've got the symbols here.

Can you see what element that spells? That was carbon.

Well done if you worked out that puzzle.

Right well that is all of the tasks for today.

Fantastic work on this lesson.

You are now an expert on atomic structure, so really big well done.

Let's summarise what we've learned today.

The atom is composed of protons, neutrons, and electrons.

Protons and neutrons both have mass and are located in the nucleus.

Electrons have negligible mass and are located in shells surrounding the nucleus.

Protons are positively charged, neutrons are neutral and electrons are negatively charged.

Atomic symbols show us the atomic mass, atomic number, and chemical symbol.

We can use atomic symbols to deduce the number of protons, neutrons, and electrons.

Fantastic work today.

Hope you enjoyed the lesson.

Now have a go at the exit quiz to see how much you've learned today.

Brilliant work and I'll see you next time.

Thanks for using the Oak National Academy.