Lesson video

Welcome to today's lesson on atomic structure.

We're going to be referring to the mass of an electron as very small in this lesson.

It's part of the "Unit: atomic structure and the periodic table." My name is Mrs. Mytum Smithson, and I'm so pleased that you've come along to learn with me today.

I think that this is sometimes a tricky topic for students, however, we're going to work through it step by step, so you have nothing to worry about.

By the end of the lesson, you should be able to describe the physical characteristics of atoms, protons, neutrons, and electrons.

Here are the keywords for today's lesson, electron, proton, neutron, nucleus, subatomic.

On the next slide, there's some sentences that include these keywords.

If you wish to pause that slide and have a read, feel free to do so.

Here's the outline for today's lesson.

It consists of two learning cycles.

First learning cycle is about subatomic particles, and the next one is about physical characteristics of an atom.

Don't worry at this stage if you don't understand what these mean, because we're going to go through this bit by bit.

First learning cycle is subatomic particles, so let's get learning.

An atom is the smallest unit of matter and everything's made up of atoms. So if you took something and you zoomed in on it enough, you would eventually come across an atom.

And an atom is made up of three subatomic particles, protons, electrons, and neutrons.

Each element has got a different number of subatomic particles that's unique to it.

What does that word subatomic mean? Well, sub is from the Latin meaning below or smaller than, and atomic means from an atom.

So today we're going to be looking at the three subatomic particles, so the three particles that are smaller than an atom.

These are protons, electrons, and neutrons.

What I'd like you to do now is name the three subatomic particles.

Is it a, atom, proton, electron, b, atom, nucleus, element, c, neutron, proton, electron, d, element, electron, atom? Pause the video for some thinking time.

Press play when you've got your answer.

So well done if you said that the three subatomic particles were c, that is a neutron, a proton and electron, those are the three particles that are smaller than an atom.

That is what an atom is made up of.

Here's our image of an atom.

It's not drawn to scale, and we're going to go on to talk a little bit more about that later on in the lesson.

And we're going to take a look at the centre of this.

Now the centre of this is called a nucleus, and in the nucleus you're going to find two of those subatomic particles.

You're going to find the neutrons and the protons and around that, so orbiting, which just means going around.

So orbiting the nucleus in the shells are electrons, and the electrons move around the nucleus and the nucleus consists of neutrons and protons.

So where would you find the protons? Here, here or here? Pause the video for some thinking time, press play when you've got your answer.

Well done if you said that you would find the protons in the centre of the atom.

That's called the nucleus.

Well done if you got that one right.

The other two that were circled were the electrons and they're in shells orbiting around the nucleus.

The subatomic particles have got different charges and all this means is that a proton is positive.

So usually the way I remember this is proton begins with a P and positive also begins with a P.

So protons are positive.

Then the electrons, they are negative.

So the electrons are negative, -1 charge on an electron.

And finally the neutrons are neutral.

Sometimes this is written as zero.

Sometimes it's written as neutral.

So neutrons are neutral.

That starts with the same letter, so that's a good way to remember that, neutrons are neutral.

What is the charge on an electron? Is it a, -1, b, 0, c, +1? Pause the video now for some thinking time, press play when you've got your answer.

Well done if you said it's a, it's -1, an electron has a negative charge.

So protons have got a relative mass of one.

Electrons have got roughly a relative mass of 0.

0005.

That is very small.

All this means is if you've got about 2,000 electrons, they would have the same mass as a proton.

And finally, neutrons have a relative mass of one.

So they've got the same mass as a proton.

So protons and neutrons in the centre in the nucleus of the atom have got the mass and electrons have got a relatively small mass of 0.

0005.

So that's very small.

A quick check for understanding now, what is the mass of an electron? Is it a, -1, b, minus 0.

0005, c, 1 or d, very small 0.

0005.

Pause the video for some thinking time.

Press play when you've got your answer.

Well done if you said that they're very small, a and b have got negative values and you can't have a negative mass and c, a mass of one, well that's the mass of the proton or the neutron.

So it is very, very small.

0.

0005 is a mass of an electron.

Now I've got another check for understanding here.

A true or false this time.

So true or falses, most of the mass of an atom is found in the nucleus, is that true or is that false? Pause the video to have a think, then press play when you've got your answer.

Well done if you said that that is true, most of the mass of an atom is found in the nucleus.

Now I want a justification for that.

So let's justify your answer, you've got two choices.

All subatomic particles have a relative atomic mass of one or the protons and the neutrons are found in the centre of the atom, the electrons are found in shells.

Pause the video now for a think, then press play when you've got your answer.

Well done if you said that the protons and the neutrons are found in the centre of the atom, the electrons are found in shells.

So the protons and the neutrons have both got an atomic mass of one.

So that's why most of the mass of the atom is found in the centre, is found in the nucleus.

Now we're going to summarise our knowledge in this task.

So I'd like you to complete the following table.

So we've got a column for the subatomic particles.

One subatomic particle has been completed for you, got the electron in there.

Location, so where are you going to find these subatomic particles? We've got one location written there, which is a nucleus, and then we've got charge.

So what charge are they? We've got one there, which is written plus one, so positive one, and then you've got two other possible charges and you need to write those in there.

And finally, the mass.

So how much mass do the subatomic particles have? Pause the video now and complete the task, then press play and we'll go through the answers.

Well done for working hard and completing that task.

I hope you got on okay.

So let's name the three subatomic particles.

We've got protons.

I'd already given you electron, and we've got neutrons as well, and where are we going to find them? So we're going to find the proton in the nucleus.

So these two subatomic particles in the nucleus, they're the protons and the neutrons and orbiting around the nucleus or moving around the nucleus in shells, we're going to find the electrons.

So the electrons are in shells.

Then we've got the charge, so we've got proton, Remember I said, protons were positive, P and P, protons are positive, electrons are negative, so that's minus one.

And neutrons sounds like neutral because they've got no charge.

So you're going to get that one right if you wrote zero or no charge.

Both are acceptable answers.

And for the mass, so the mass of the proton is one, the mass of an electron is 0.

0005 or very small.

And the neutron, we had already given you that one as one.

Remember, most of the mass is in the centre of the atom, in the nucleus, so most of the mass is in the nucleus.

So the two subatomic particles with mass are protons and neutrons, we find those in the nucleus.

Well done if you've got all of that information correct.

Here's part two of task A.

What I'd like you to do now is correct the errors in the diagram that Izzy has drawn.

So she's drawn a diagram of an atom and she's labelled it up and drawn it incorrectly.

I want you to correct the errors in this diagram that Izzy's drawn.

So pause the video, complete this task, and then press play when you've got your answer.

Well done for working really hard and completing that task.

Let's see how you got on.

So here were the errors.

So the shell and the nucleus labels were swapped.

So the nucleus should be the part in the middle that contains the neutrons and the protons and the outside is the shell, so that's the circle, that's the shell and actually contain the electrons.

She had swapped the proton and neutron labels over.

So the protons should be labelling up a positive and the neutron is labelled up with neutrals, subatomic particles.

Then we've got the electrons and they're labelled with a negative sign, not a positive sign as she had done.

So your electrons should be negative in the shells, neutrons should be neutral, protons should be positive, and the neutrons and protons are in the nucleus.

So, well done, if you've got that correct, you've worked really hard and you're very knowledgeable now about subatomic particles.

Well done for working really hard during the first learning cycle called subatomic particles.

Now we're moving on to physical characteristics of an atom.

Now we're going to have a look at the physical characteristics of atoms. So an atom has no overall electric charge and this is because it contains equal numbers of protons and electrons to balance out the charges.

So let's have a look at an example of this.

So we've got a lithium atom.

A lithium atom has got three electrons, three protons, and four neutrons.

So here's our three electrons and the charge you can see is cancelled out by those three protons and then we've got some neutrons in there.

So the three negative electrons cancel out the charge of the three positive protons, but the neutrons have got no charge.

So it doesn't matter if you've got three or four because the neutrons have got no charge, so they don't affect the overall charge of an atom.

But you will always have on an atom the same number of electrons and protons in an atom and that's what makes it neutral.

So here's a another example.

So this is boron this time.

Now sometimes the atoms have the same number of electrons, protons, and neutrons, but not always.

So this example has got five electrons, five protons, and six neutrons.

So if we have a look here, here's our five electrons.

So we've got five negative charges and they're cancelled out by those five positive charges.

Then if we have a look, we've got six neutrons.

So the five negative electrons cancel out the charge of the five positive protons.

But as the neutrons don't have a charge, they do not affect the overall charge of an atom.

Let's have a quick check for understanding.

An aluminium atom has 13 electrons, 13 protons, and 14 neutrons.

What is the overall charge of an aluminium atom? Is it minus one, is it zero? Is it plus one or is it plus 26? Pause the video for some thinking time.

Press play when you've got your answer.

Well done if you said "Zero," those 13 electrons are negative and the 13 protons are positive.

So they cancel each other out and it doesn't matter about the number of neutrons because they're neutral, they don't affect the overall charge.

Well done if you got that one correct.

Atoms are really very small.

They have a radius of about 0.

1 nanometers or 1 times 10 to the minus 10 metres.

Very small indeed.

And the nucleus is even smaller than an atom.

So when we were drawing diagrams earlier, we said that they weren't drawn to scale.

What that meant is that the nucleus wasn't drawn to scale In comparison to the shells, the radius of the nucleus is less than 1/10,000th the size of an atom.

So that's about 1 times 10 to the minus 14 metres.

Incredibly small.

The nucleus is about 10,000 times smaller than the atom.

So just to give you an idea of scale, if we took an atom and we scaled it up so that the atom was the size of a football stadium, just like the one that's pictured here, the nucleus would only be the size of a marble or a small grape.

So you can see there's a big difference in the size of the atom and the size of the nucleus.

I've got a quick check for understanding for you.

True or false, the radius of a typical atom is very small, it is approximately 0.

1 nanometers or 1 times 10 to the minus 10 metres.

Pause the video now for some thinking time.

Press play when you've decided if that statement is true or false.

Well done If you said that that statement is true.

Now I want you to justify that.

So the typical size of the radius of the nucleus is 1 times 10 to the minus 14 metres of an atom is 1,000 times smaller than a typical atom.

All the typical size of the radius of the nucleus is 1 times 10 to the minus 14 metres of an atom and it's 10,000 times smaller than a typical atom.

Pause the video now for some thinking time, press play when you've got your answer.

Well done if you said, b, the typical size of the radius of the nucleus is 1 times 10 to the minus 14 of an atom and it's 10,000 times smaller than that of a typical atom.

Well done for working really hard so far this lesson.

Now we're going to look at this table of information.

I'd like you to complete the table of information.

You can see it's got some missing information.

It's a list of elements.

So we've got a list of elements and it's telling you how many electrons there are in that element, how many protons there are and how many neutrons there are.

So we've got the three subatomic particles there, and we're going to look at the impact on the overall charge of the atom.

So what I want you to do is complete the table of information, pause the video now, complete that task and press play when you've got your answers.

Well done for working really hard on that one.

So all you've got to do now is some simple maths.

So when we look at beryllium, if I've got four electrons, that means I've got four negatives.

I've got four positives because I've got four protons and I've got five neutrons which don't impact the overall charge of an atom.

So the four electrons cancel out the four protons, giving me an overall charge on the atom of zero.

Then we're going to have a look at nitrogen.

We've got seven electrons, seven protons, seven neutrons, and all that means is that we've got seven negatives and seven positives and they cancel each other out.

Remember, the neutrons don't have any impact on the overall charge of the atom, so that is indeed zero.

Then if we have a look at sodium, again, we've got 11 electrons, they're negative and we've got 11 positives.

And the neutrons 12, it doesn't matter how many of those we've got because they don't impact on the overall charge of the atom.

So that is again, zero.

Now this time round, we've got an overall charge of the atom of zero, and we're gonna have a look there.

We've got 20 neutrons.

Now that doesn't impact the charge at all.

If we've got an overall charge of zero and we've got 20 electrons, that's a negative.

So we've got 20 negatives.

We must have 20 positives, well done if you've got that one.

Slightly difficult.

And again, similar thing here with the oxygen.

If we've got eight positives, we must have eight negatives, so we must have eight electrons, 'cause the overall charge on that atom is zero.

Again, it doesn't matter how many neutrons we've got because they're neutral and they don't affect the overall charge.

So finally, if we've got nine electrons, we must have an overall charge of zero on the atom and we must have done that by having nine protons.

So well done if you managed to get all of that information correct.

There is no overall charge on an atom because the electrons always cancel out the protons in atoms, well done for working really hard on that, well done for working really hard this lesson.

What we're going to do now is we're gonna have a look at this task.

This is part two of task B.

Complete the sentences using the information in brackets.

So atoms are very big or very small.

They have a radius of approximately 1 times 10 to the minus 14 metres or 0.

00001 nanometers or 1 times 10 to the minus 10 metres or 0.

1 nanometers.

So I want you to choose either the size before the slash or after the slash.

C is the nucleus of atom is even smaller or a similar size.

And D, they have a radius of approximately 1/10,000th the size of an atom, or 1 times 10 to the minus 10 metres or 0.

1 nanometers.

Again, you're either choosing the size before that slash or after that slash.

The atom is 10,000 or 1,000 times bigger than the size of a nucleus.

Pause the video, complete the task, press play when you want to go through the answers.

Well done for completing these sentences.

Now let's go through the answers.

So atoms are very small.

They've got a radius of approximately 1 times 10 to the minus 10 metres or 0.

1 nanometers.

The nucleus of an atom is even smaller.

They have a radius of approximately 1/10,000th time of an atom, and the atom is 10,000 times bigger than the size of the nucleus.

So you can see there that the atom is very much bigger than the nucleus.

That nucleus is really, really tiny.

So well done if you've got all of those correct.

Okay, here's part three of task B.

Imagine you were asked to make a model of an atom.

Explain why you could not make it to scale.

So I want you to think about making a model of an atom, physical model of an atom, and you can use a labelled diagram and the following prompts to help you.

So, atom, nucleus, 1/10,000 or 10,000, larger or smaller.

So we've got some prompts there to help you.

You can use some of those words or all of those words, and I want you to tell me why you couldn't make a scale model of an atom.

Pause the video now, complete the task.

Press play when you've got your answer.

Well done for completing part three of task B.

This has definitely been the trickiest task so far of this lesson.

So you might have drawn a diagram a little bit like this, showing the nucleus and the atom.

Now what you've gotta think is, could you draw this to scale? Well, no, you couldn't.

And here's the reason why.

The atom is so much larger than the nucleus, or you could have written it, that the nucleus is so much smaller than the atom.

If we have a look at the size, an atom is approximately 10,000 times larger than the nucleus and the nucleus or you could have said that the nucleus is 1/10,000 times smaller than the atom.

So because of the difference in scale, it would be very, very difficult to make a model to show the nucleus and the atom to scale.

So your answer will probably sound a little bit like this.

The main point that you're making is that the nucleus is significantly smaller than the atom.

Well done if you managed to get that right, you've done really, really well.

Here's a summary of today's lesson.

Electrons have a relative charge of minus one that attracts 'em to the atomic nucleus and roughly a relative mass of 0.

0005, very small.

Protons are found in the atomic nucleus, have a relative electric charge of plus one and a relative mass of one.

Neutrons are found in the atomic nucleus, have no electric charge and a relative mass of one.

An atom has no electric charge as it contains equal numbers of protons and electrons to balance the charge.

The atom has a nucleus surrounded by electrons with a nuclear radius being much smaller than that of the atom.

Well done for working really hard throughout this lesson.

I think there was some tricky concepts in there.

However, I'm sure that you've done really well and are now an expert on atoms. You should have learned about the subatomic particles and their masses and their charges and where you would find them.

Well done for working really hard this lesson.