Lesson video

Welcome to today's lesson on the modern periodic table and electron configuration.

It's part of the unit atomic structure in the periodic table.

My name's Mrs. Martin Smithson, and today we're going to look at the modern periodic table.

We're going to work together to to explain how it's laid out and organised, and be able to draw the electronic configuration of the first 20 elements.

Don't worry if you don't know about these concepts.

We're going to work through some exercises step by step, and by the end of it, you'll be far more confident about the words electronic configuration, and the way that the modern periodic table is laid out.

Here are today's key words, electron shell, electron configuration, period, group.

On the next slide, there's some sentences explaining what these mean.

So if you wish to read them, pause the video and then press play when you're ready to start the lesson.

Today's lesson about the modern periodic table and electron configuration consists of two learning cycles.

Firstly, we're going to learn about how the electrons are laid out in electron configuration, and then we're going to look at the periodic table arrangement.

So let's get going with electron configuration.

Here's diagram of an atom and it consists of a nucleus, which contains the protons and neutrons, and they're in the centre of the atom.

You can see those labelled up.

And orbiting around that, so going around the nucleus are the electrons and they're in the electron shells and they contain the electrons, which have got a specific energy orbiting around the nucleus.

The electronic configuration of an atom shows how electrons are arranged in shells.

So here are the rules.

The electrons occupy the lowest energy level first, and this is the shell that's nearest and nucleus.

And then they fill the shells as following.

So the first shell can fit two electrons in it.

Once that's full, we are going to move on to the second shell, and that shell can have up to eight electrons.

If we've got more than 10 electrons, we'll need to go into a third shell, and that will also contain up to eight electrons.

So electrons can be drawn as either dots or crosses for our diagrams. So here's lithium, and here's the example of, as a cross diagram, and there's a dot diagram.

So lithium's got three electrons.

Two are drawn in the first shell and one is drawn in the next shell.

So you can see here we've got the first two are in that first shell, which is closest to the nucleus.

Remember, we're going to fill from the inside to the outside.

And then because lithium's got three electrons, we must put another shell on, so a second shell.

And we're going to place that third electron in that second shell.

So the first 20 elements, it gets a little bit more complicated and you're only required to know about the first 20 for this lesson.

We're going to take a look at a couple of examples.

The first one's chlorine, it's got 17 electrons in total.

So we want to know how those are arranged around the nucleus.

So remember, the first shell can fit up to two electrons in it.

So first of all, we're going to draw the symbol for chlorine.

We're going to draw the shell, and then we're going to draw those electrons at the top and at the bottom for the first shell.

Now that shell's full.

So then we're going to move on to the second shell, and the second shell can hold up to eight electrons.

So we draw our shell and we draw our electrons on there.

I find it easy to pair them up at the top on the bottom and either side of the symbol.

I find that makes it much easier to count 'em up.

So then you can see we've used up 10 electrons.

Now for the final shell, because chlorine's got 17 electrons and we've used 10 of them, we're going to draw seven electrons in this shell.

So the third shell, although it will hold up to eight electrons, we've only got seven to put in there.

So again, we'll draw the shell and then we'll draw those electrons at the top and side to side, and then just one at the bottom.

So you can see here that this is chlorine and in total we've got 17 electrons.

Now if we were to want to write this shorthand, we could use this.

So we've got a curly bracket and then we've got a number two, number eight, number seven, and then close the bracket.

Now what this means is we've got two electrons in the first shell, eight in the second shell, and seven in the third shell.

So that's a shorthand way of writing the electronic configuration for chlorine.

Let's have a look at the most complicated example now that you are going to be asked to draw.

So here's calcium.

Now calcium's got 20 electrons in total.

So again, we've got 20, so we're going to put two in the first shell.

So we'll draw the symbol for calcium and we'll draw the shell.

We're going to add two electrons in there.

The second shell has got up to eight.

So now we've got to draw another shell, and then we've got to draw those eight electrons.

So now we've got 10 electrons, and we need to put 20 in for calcium.

So our third shell is going to have up to eight, and we are gonna put eight in it 'cause now we've got 18 electrons and you can see if I draw them top and bottom side to side, it makes it much more simpler to see that you've got the right number of electrons in there.

And then finally, the fourth shell.

Now the fourth shell, we've only got two electrons to put in there.

So we're going to put two electrons in that fourth shell.

We're going to put those at the top and at the bottom.

Now we can also write this in the shorthand way.

So we're going to look how many electrons are in the first shell.

There's two, then the second shell, there's eight, the third shell eight, and the fourth shell has got two in it.

So we're going to write this bracket two, eight, eight, two, and then close the brackets.

So well done if you've managed to follow that.

Now a quick check for understanding.

Which shell should be filled first? Is it the one closest to the nucleus? Is it the second one or is it the third one away from the nucleus? Pause the video, choose A, B, or C, and then press play.

And I'll tell you the answer.

Well done if you said it was A.

Indeed A is the one that's closest to the nucleus and we feel from the inside to the outside.

So we fill from the ones closest to the nucleus all the way out.

Well done if you got that one correct.

Here's another check for understanding.

Beryllium has four electrons.

Select the diagram or diagrams that show or shows the electronic configuration of beryllium correctly.

Pause the video for some thinking time, press play and we'll go through the answer or answers.

Well done if you said that A and C show the electronic configuration of beryllium correctly.

Remember, electrons can be represented by either crosses or dots, but not a mixture of both.

Sulphur has 16 electrons.

Select the diagram or diagrams that show or shows the electronic configuration of sulphur correctly.

Pause the video for some thinking time.

Press play when you got your answer or answers.

Well done if you said it was B.

Indeed, sulphur has got 16 electrons, so we're going to put two in the first shell and then that's full, eight in the next shell and then that's full, so we've got 10, which leaves us with sixth to place in the outer shell.

So well done if you've got that correct.

I'm going to do another example.

I'm gonna choose neon.

And then you're going to do an example of an element that I tell you in a minute.

So neon's got 10 electrons.

Draw the electronic configuration of neon, then write the shorthand notation.

So here's neon, it's got 10 electrons in total, so I want to put two in the first shell.

If I don't know the symbol, I'm gonna look that up on the periodic table.

Then I'm gonna put eight electrons in the second shell and that gives me a total of 10 electrons.

So I've used up all of my electrons can't put anymore shells on.

Now electrons don't need to be paired up.

I just find it makes it easier to cancel, less opportunities to make mistakes.

'Cause if you have a look at this one, this is the same element.

It's neon, it's got eight round the outside, but you can see that they're much more difficult to count.

Now we're going to write the shorthand notation.

So the shorthand notation, we've got two in the first and then eight in the second shell.

So we're going to write this two, eight.

What I'd like you to do is nitrogen has got seven electrons.

Draw the electronic configuration of nitrogen, then write the shorthand notation for it.

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

Well done them for completing that check for understanding.

So here's nitrogen, it's got the symbol N.

and remember it must be a capital N.

We're going to draw the first shell.

Then we're going to place two electrons on there.

So we've got a total of seven electrons.

So what we're gonna do is we're gonna draw another shell.

Now this can hold up to eight electrons, but as we've only got seven in total and we've already used two of them, we are gonna put five on there.

Then we're going to look at drawing the shorthand notation.

So we've got two electrons on the first shell and five on the next.

So we would write this two, five.

You must put those brackets on there too.

So well done if you've got that correct.

Here's task A.

It's got two parts to it.

So the first thing I want you to do is draw the electronic configuration for the following elements.

I've given you the name of the elements, the symbol of the elements, and the total number of electrons.

Then what I want you to do is when you've drawn the electronic configuration out in full, I want you to write the shorthand electron configuration for these elements.

So pause the video, complete the task, then press play and we'll go through the answers together.

Well done for completing that task.

Let's go through the answers.

So we've got hydrogen.

Hydrogen must be a capital H.

Got one electron.

Beryllium, capital B, lowercase e, two in the first shell and two in the second shell.

We've got carbon, we've got two electrons in the first shell, four electrons in the second shell.

Fluorine, we've got two electrons in the first shell and we've got seven electrons in the second shell.

Obviously it's easier to count if you've paired them up.

And then we've got magnesium, which has got two in the first shell then we've got eight in the second shell, and then finally two in that third shell.

Now we're going to look at the shorthand notation for this.

So hydrogen, we just do a one in brackets.

Beryllium we'd write two, two in brackets.

Carbon we'd write two, four.

Fluorine, We'd write two, seven.

Magnesium we'd write two, eight, two.

Well done if you've got all of those correct.

Let's go through some more answers.

So we've got silicon here.

So silicon's got two in the first, eight in the next, and then four in that third shell.

Chlorine we've got two in the first shell, eight in the second shell and seven in that outer shell, that third shell.

We've got argon that's got two in the first shell, eight in the second shell, and eight in that third shell.

And we've got calcium.

Now this is the biggest one that I'm ever gonna ask you to draw.

So we've two in the first shell, then eight in the second shell, then eight in the third shell, and two in the fourth shell.

So let's do the shorthand notation for these now.

So silicon should read two, eight, four.

Chlorine is two, eight, seven.

Argon is two, eight, eight.

And calcium is two, eight, eight, two.

Well done if you've managed to get all of those correct, you're doing really well.

We've now looked at electron configuration.

Now we're going to move on to the periodic table arrangement.

The periodic table is ordered by increasing atomic number.

So this is the bottom number on this periodic table.

It's the smaller of the two numbers.

We're gonna look at hydrogen, hydrogen's got atomic number one.

So that's got one proton.

Helium's got two, lithium's got three, beryllium's got four, next one is five and six, which is boron and carbon.

Then we continue along.

You can see that they increased by one each time.

Once we get to neon, that's got 10 protons.

Then we're gonna go staff another row, and that's sodium that's got 11.

I'm gonna continue this.

You can see that the numbers continue all the way up to 118, which is the final element on the periodic table.

So it is ordered by increasing atomic number.

So that's the number of protons.

Elements can be classed as metals on non-metals according to their position in the periodic table.

So we've got this divide.

Sometimes it's called the stairs, starts under boron and above aluminium and it zigzags down.

And on the left hand side of that, these are all the metals.

You can see that there's many more elements that are metals.

And then these are all the non-metals on the right hand side of those stairs.

So on the right hand side of the periodic table, we've got the non-metals, on the left hand side, we've got the metals.

Now the periodic table, it's got row called periods and columns called groups.

So the periods go from left to right and the groups go from top to bottom.

So you can see there we've got the periods labelled up and we've got the groups labelled up.

Now one of the things that a lot of people struggle with is that first period, that first period only contains hydrogen and helium.

I've got a quick check for understanding, which is group six.

So I've circled four different parts of the periodic table, which is group six.

Pause the video for some thinking time, press play when you got the answer.

Well done if you said that D was group six, remember groups run from top to bottom in columns.

So that's group six.

Which is period four? Pause the video for some thinking time, then press play when you've got your answer.

Well done if you said that that was A.

A is period four.

Remember periods run from left to right.

They are rows.

The position of an element in the periodic table is linked to its arrangement of electrons and to its atomic number.

So the group number tells you the number of electrons in the outer shell.

For example, everything in group six has got six electrons in their outer shell.

So here's oxygen, you can see there it's got six electrons in its outer shell.

So the outer shell is the one that's furthest away from the nucleus.

And you can see here that's we've got sulphur, sulfur's got six electrons in its outer shell, that's the one that's furthest from the nucleus and it's got six electrons in its outer shell.

So those two elements would be in group six.

Anything that's got four electrons in his outer shell would be in group four.

Anything with five electrons in his outer shell would be in group five.

The only one that's a little bit confusing is that everything in group zero has got a full outer shell.

So we don't say group eight.

And the reason why we don't say group eight is because of helium.

So helium has got a full outer shell, and it's got two electrons in it, and here's neon, neon's got eight electrons in it's outer shell and that is full.

So all you've got to remember is everything in group zero has got a full outer shell.

The period number tells you the number of shells occupied by electrons.

For example, everything in period two has got two shells occupied with electrons.

So here's boron.

You can see that boron's got two electrons in its first and three in its second.

So it is got two shells that have got electrons in.

And we've got oxygen here.

Oxygen has got two electrons in its first shell and then it's got six electrons in its second shell.

It's in period two because it's got two shells with electrons in it.

Everything in period three has got three shells that are occupied with electrons.

So here's sodium.

You can see there that it's got three shells that have got electrons in.

And we've got phosphorus there.

That's also in the same period for the same row on the periodic table, because it's got electrons that are in three shells.

This image shows the electronic configuration of fluorine, what group is fluorine in? Pause the video for some thinking time.

Press play when you've got your answer.

Well done if you said that fluorine is in group seven, it is got seven electrons in its outer shell.

So it's in group seven.

This image shows the electronic configuration of boron, what period is boron in? Pause the video for some thinking time.

Press play when you've got your answer.

Well done if you said that boron is in period two, it's in period two because it's got two shells that have got electrons in.

So two occupied shells.

Well done if you've got that one right.

Which element or elements is/are in group three.

So pause the video, write your answer or answers, and press play and we'll go through the answers together.

Well done if you said that group three was elements B and C.

So the groups are the columns.

So that's those two elements are in group three.

Well done if you've got that one right.

Which element are elements is/are in period two? Pause the video now for some thinking time and then press play when you've got your answer.

Well done if you said that period two is elements A and C.

So remember that first period consists of hydrogen and helium.

And so that first row, so that first horizontal row is period one and then the next horizontal row is period two.

Well done if you've got that one right.

Here's task B.

What I want you to do is match up the sentences.

So we've got on a periodic table, the elements are, on a periodic table the groups are, on a periodic table the periods are, and then we've got the vertical columns, the horizontal rows organised in increasing atomic number organised in decreasing atomic number.

So you've got three sentences and you've got four options to choose from.

So pause the video now complete the task and then press play and we'll go through the answers.

Well done for completing that task.

On a periodic table, the elements are organised in increasing atomic number.

On a periodic table, the groups are the vertical columns.

On a periodic table, the periods are the horizontal rows.

So remember, groups are from top to bottom and periods are from left to right.

So well done if you got that correct.

I would like you now to do part two of task B, help Aisha complete her sentences about the period number and the group number.

So here's her sentence starters.

The period number is the same as.

The group number is the same as.

And she's got some friends to help her out.

So Sophia's saying the number of shells with the electrons in.

Andeep saying the number of electrons in the outer shell.

John's saying the total number of electrons.

So complete her sentences.

So pause the video now once you do that, then press play and we'll come back and go through the answers.

Well done for completing that task, helping Aisha complete her sentences about the period number and the group number.

So the period number is the same as the number of shells with the electrons in.

So Sophia gave her the answer there.

And the group number is the same as the number of electrons in the outer shell.

So that's just the number of electrons in the outer shell, not the total number of electrons like John said.

Well done if you got that correct.

Now for part three of task B, I want you to use your periodic table to name these elements.

So name the element that has a full outer shell and is in period two, has seven electrons in the outer shell and is in period three, has five electrons in the outer shell and three shells occupied by electrons, is in period four and in group one, has one shell and it is full of electrons, has a total of four shells occupied by electrons and two electrons in the outer shell.

So I want you to pause the video, complete this task, and then press play and we'll go through the answers together.

Well done them for completing part three of task B.

So using your periodic table, you're gonna name the element that I'll say full outer shell.

So the one that's got a full outer shell, so that's something in group zero and is in period two.

So you're going to look for the second period down.

So that is neon.

Has seven electrons, so anything that's got seven electrons in its outer shell is in group seven and is in period three.

So you're looking for the third row down there.

So that is chlorine.

Has five electrons in the outer shell.

So remember, the number of electrons in the outer shell is the same as the group number.

So that's group five.

And three shells, so that's the third row down occupied by electrons.

That should take you to aluminium.

So something that's in period four and in group one.

So all you've got to do there is look down group one until you've got the fourth element down, and that is potassium.

Has one shell and is full of electrons.

So you're looking there for the full electrons.

So this one is helium, so that's in group zero 'cause it's full of electrons.

And has a total of four shells.

So we're looking for the fourth row down there.

So the fourth period, and it's got two electrons in it's outta shell.

So that's group two.

So that should be calcium.

So well done if you got that correct.

Well done for working hard this lesson.

This is part four of task task B.

So using your periodic table, I want you to complete this table of information.

So you can see we've got the element.

We've got number of protons, number of electrons, number of electrons in the outer shell, the group number, number of shells containing electron, and the period number.

And then we've got elements, helium, beryllium, carbon, fluorine, magnesium, silicon, potassium, and argon.

All you've got to do is use your periodic table to complete the information.

So pause the video.

Once you do that, press play and we'll go through all of these answers together.

Well done for completing this task.

I hope you've got an okay.

So we've got helium.

So the clue there is that you've got the two protons there, means you must have two electrons.

The number of electrons in the outer shell is also two, and the group number is zero 'cause that's a full outer shell.

The number of shells contain electrons is one, that means it's in period one.

So now we've got beryllium, four protons, four electrons.

Gives us two electrons in the outer shell 'cause we're gonna put two in the first shell, the second shell is going to be two.

The group number is therefore two 'cause there's two electrons in the outer shell.

It contains two shells that have got electrons in them, which means it is in period two.

So for carbon, if it's got six electrons, must have six protons.

Number of electrons in the outer shell, it's got four because it's got two electrons in the first one and four electrons in the next shell.

That number of electrons in the outer shell is going to match the group number and the number of shells containing electrons is two, and that's going to match the period number.

So you'll see the patterns starting to emerge here.

So fluorine, number of protons, it's got nine protons 'cause they've got nine electrons, number of electrons in the outer shell, it's got seven in the outer shell which means that it's in group seven.

Number of shells containing electrons.

So there's two and that matches up with the period number.

So magnesium, that's got 12 protons and 12 electrons.

You'll notice that they're both the same.

The number of electrons in the outer shell is the same as the group number and the number of shells containing electrons is the same as the period number.

That's three 'cause you'd put two in the first, eight in the next, and then you'd add those up and you'd say, I've got 10, so I've got two more left for the third shell, and I put two in that third shell, meaning it's in group two.

So silicon.

Now we know that the number of electrons in the outer shell is four.

So we can find out the number of protons in electrons from the periodic table.

That's 14.

The group number therefore is four because that's going to match the number of electrons in the outer shell.

The number of shells containing electrons is three.

So three shells contain electrons which means that it's in period three.

So for potassium, 19 electrons here.

So there's quite a lot of electrons.

Number of electrons in the outer shell are one because it's in group one, and the number of shells containing electrons are four.

And that's period number of four.

So finally, argon, it's got 18 protons, 18 electrons.

The number of electrons in the outer shell, that's eight, and that means it's a full outer shell.

So that makes it in group zero.

So anything with a full outer shell is in group zero.

The number of shells containing electron for this is three which means that the period number is also three.

So well done if you saw that, those patterns are emerging.

So the number of electrons in the outer shell is the same as the group number, unless it's a full outer shell in which case it's in group zero.

Number of shells containing electron is the same as the period number.

So well done if you've got all that correct.

Here's a summary for the modern periodic table and the electronic configuration.

The periodic table is ordered by increasing atomic number, so that's the proton number.

The periodic table is split into periods and groups.

The position of an element in the periodic table is linked to its arrangement of electrons and atomic number.

Elements can be classed as metals or non-metals according to their position in the periodic table.

A useful model of atoms shows electrons arranged in shells around the nucleus.

Well done for working really hard this lesson.

I hope you're now confident about drawing the electronic configuration for the first 20 elements, and also being able to link this electronic configuration to where you would find them on the periodic table.

So well done for working really hard.

I hope to see you again soon.