Lesson video

Hello.

Welcome to this lesson entitled "Groups of Elements in the Periodic Table" from the topic "Patterns in the Periodic Table".

My name is Mr. Gundry and today we're gonna be going through this lesson all about how the periodic table is arranged, and I hope you're looking forward to it 'cause it's quite an exciting lesson.

The aim of today's lesson is to be able to identify and describe properties of some different groups of elements in the periodic table.

We're also gonna dive into a little bit on atomic structure and we're gonna learn about how the periodic table is aligned with atomic structure.

There are some keywords from today's lesson.

They are periodic table, group, period and transition metals.

And on the next slide you'll find some information about how they're defined.

But we're just gonna cover that as we go through the lesson.

This lesson is split into two parts.

The first part we're gonna look at the foundations of the periodic table and in the second part of the lesson, we're gonna explore groups and their properties.

So let's start by looking at the basics of the periodic table.

So you might already know that the periodic table actually houses 118 different elements.

Only about 92 of those are naturally occurring.

The rest are manmade, but at the moment we understand there to be 118 different elements.

Now we know that the periodic table can be split into three different sections.

We can split it into metals, non-metals and metalloids.

Remembering that metalloids are substances that have similar properties to metals, but also similar properties to non-metals.

At GCSE, we don't tend to include metalloids in that description, we tend to just split it in half between metals and non-metals and metalloids generally get included in the non-metal section on the periodic table.

However, as you may have guessed, you can see on the periodic table shown that there are some numbers down the side and across the top.

This isn't actually the main way that we split the periodic table.

We don't really split it just based on metals and non-metals.

There is another more sophisticated way that we split the periodic table.

It's very delicately designed.

It's very interesting.

It's one of my favourite parts of chemistry.

So you might have heard of a chemist, a scientist known as Dmitri Mendeleev.

He spent about 10 years of his life trying to order the elements in the mid to late 1800s.

At that time, scientists were only aware of 63 elements.

Remember, we now know there are 118.

There is a legend behind the discovery of the arrangement of periodic table elements that we have today, that Mendeleev went to sleep one night after arranging elements on cards.

He played a game of chemical solitaire and he stayed up for three days straight, I think is the legend had as it goes and then finally fell asleep.

And once he was asleep, the cards rearranged themselves for him in his dream, he woke up and that was it.

That was the arrangement of the periodic table.

Now that makes it sound very magical and very mystical.

However, there were things that Mendeleev didn't get right, and that's because he didn't have all of the information and you'll learn more about that later.

But today we're gonna focus on the things that he did get right, which is why his idea of the periodic table was accepted by scientists worldwide.

And there were many other scientists that put ideas out there that weren't accepted.

So his model was accepted because, he placed not only on the elements of atomic weights, which a lot of other scientists were doing, he placed the elements in an order based on their properties.

That's gonna be a key theme of what this lesson later on that we're going to cover.

He also put them into groups.

Now that's really important because that's also a key theme of what we're gonna talk about later.

Dmitri Mendeleev was a very humble man.

He was a very open ideared guy.

And he had an idea that there was going to be more elements that were discovered.

They didn't have the technology at the time, to be able to fully understand the world around them.

And so where there were gaps that he found in his periodic table, he didn't just move elements to fill those spaces like other scientists had done.

He suggested that they were going to be elements that would still be discovered.

And not only did he suggest that, but he also predicted the properties of those elements.

One of those elements, eka-aluminum, which we now know to be gallium I believe, or germanium one of the two.

He predicted both of them.

He had predicted their properties.

And one of the main pieces of evidence that was used to accept this periodic table, is that shortly after this periodic table was proposed, we discovered that element and it had almost exactly the same properties that Mendeleev had predicted that they would have.

So true, or false for you at this stage.

Mendeleev proposed a model of ordering the elements that involved grouping them together, true or false? Well, the answer is true.

And I'd like you to read through these two justifications below and I'd like you to pick the answer that makes the most sense to justify why this is a true statement.

Pause the video whilst you read through them now and press play when you're ready to continue.

So he didn't order them by metals, non-metals and metalloids.

He ordered them based on their properties and their atomic weights.

You may have heard that elements are made up of only one type of particle called atoms. But when the periodic table by Mendeleev was proposed, we didn't know about atoms. We thought they existed, but we didn't know very much them.

And since that time we've actually learned that atoms are made up of smaller particles known as protons, neutrons and electrons.

And so when Mendeleev suggested his table, he suggested that based on just one numerical property, or atoms, their atomic weight.

But we now know that there is another numerical property.

And you may have seen this on a period at table that you've had access to maybe in your planner, or up in your classroom, that there is another number called the atomic number.

And that is a really important number as well.

And that's based on the subatomic particles within the atom.

So here is a very generalised sketch of an atom.

This is actually a sketch of an element called helium.

And we're gonna talk about now what the different coloured circles represent within this structure.

So an atom consists of some major sections.

The middle, the centre of the atom we call the nucleus, very similar to the centre, or the most important part of a cell, the nucleus.

Not the same thing, but they do mean the same thing.

The idea of it being the central parts, not necessarily true for a cell, but it is true for an atom.

That's why you'll find the two particles known as neutrons and protons.

And around the outside of the atom is where we'll find shells.

We call them these rings, we call 'em shells.

That's where you'll find the electrons.

So they orbit around the centre a bit like planets all around orbit around the star.

The period table then tells us enough information about how many protons, neutrons, and electrons, each atom of every element will have.

So let's have a look at the periodic table again then.

So this one's maybe slightly more detailed than one you've seen before.

It's got two pieces of information in each of the boxes, two numbers, one known as the relative atomic mass, and one known as the atomic, or proton number.

We've also got these rows, so that's each of the different levels horizontally as we go down.

And we've also got columns, so that's from top to bottom, that are called groups.

They're very important pieces of information.

So periods.

This tells us the number of shells, the number of rings of electrons that exist around the outside of that nucleus of each of the atoms. And then we've got groups, that tells us the number of electrons in the outermost shell.

So there's some inner shells and there's some outer shells.

The group number tells us how many electrons are in the outermost shell.

Okay, just to see whether you're paying attention.

Each row of the periodic table is called a group, true, or false? And the answer is false.

And here are two statements, I'd like you to read through both.

Pause the videos as you do so and press play when you're ready for the answer.

Well the answer is B.

Each horizontal row is actually called a period.

The columns of the periodic table are known as groups.

So, as we've just said, a period is a horizontal row on the periodic table.

In an atom, we know the electrons are orbiting around that nucleus in shells.

Here we've got a very simplified set of diagrams. We've removed the nucleus from the diagrams and we've just replaced it with the elemental symbol, again that we found on the periodic table.

We've got on the left, we've got hydrogen and helium.

They're both located in the first period.

The first row of the periodic table.

They've only got one shell of electrons, remember that's what the period number tells us.

The number of shells of electrons.

Helium is also in the first period.

It's in the first row, so it only has one shell of electrons.

Carbon on the other hand is found in the second row, the second period of the periodic table.

So it should have two shells of electrons just seen here and it's got four electrons in its outermost shell.

That's one furthest away from the nucleus because it's in the fourth group.

Those two pieces of information are linked together.

So a group is a vertical column on the periodic table.

And as we've already said, elements in the same group have the same number of electrons in the shell that is furthest away from the nucleus.

We call that the outer shell.

So hydrogen to group one has one electron, it's outer shell or on the other hand, it's in the second row of the periodic table.

So, it's got two shells of electrons, but it's in the third group.

So that tells us that there are three electrons on the outermost shell for Boron.

So we can read the periodic table from left to right, starting with hydrogen in the middle there at the top.

Hydrogen's got an atomic number of one.

That's the number at the bottom of the square.

We can see that in the key.

It tells us that it is the atomic proton number.

It also tells us how many electrons there are in the neutral atom of each element.

So we've got one proton.

That's what that tells us.

If we go over to the right as if we were reading a book from left to right, we can see helium.

It's got a number two at the bottom, that tells us that there are two protons.

We've got to the end of the row.

So like if we are reading a book, we need to start the new row.

So we go to the bottom, we go Y over one to lithium, and we can see lithium has got three protons.

Again, we'll be reading from left to right.

So we get to beryllium.

It's got four protons.

We read from left to right, we get to Boron, it's got five protons.

We are reading from left to right.

So we go to carbon.

It's got six.

Nitrogen has seven.

oxygen, eight.

fluorine nine, neon, 10.

We've got to the end of the row, so we go back to the next row down.

Starting with sodium, it has 11.

Magnesium, 12, aluminium, 13.

We can see that a periodic table in the modern era is actually arranged on an increasing atomic number, the increasing number of protons and it increases by one every time.

So which of the following statements are true about elements that are in the same group? Have a read through these statements, pause the video as you do so and press play when you're ready to hear the answer.

Well, the answers are they have the same number of electrons in their outer most shell, and they are made of atoms which are made up of protons, neutrons, and electrons.

They don't have the same number of electrons, because each atom has a different number of, sorry, each atom of different elements, has a different number of electrons.

And they don't have the same number of shells of electrons.

Actually every element in the same group has a different number of shells, or electrons.

Okay, task time.

You gonna probably wanna pause the video as you complete this task, but you've got a periodic table in front of you.

I'd like you to label the periodic table with the following labels.

You may need to colour in, or shade various sections if you are going to label metals, non-metals and metalloids.

And pause the video as you do that and press play when you're ready to see the answer.

Well, the answer is shown.

You've got six periods, they are shown from the top to bottom.

You've got groups shown left to right and we've got our metals, metalloids and non-metals shaded in three different colours.

Right then, I'd like you to describe then what is meant by the terms group and period in the context of arranging elements on the periodic table.

And just to give you a little bit of a helping hand, I'd like you to refer to electrons and electron shells in your answer.

So, pause the video now whilst you do that.

Press play when you're ready to see the answer.

So, the term group and period then mean two very specific things.

A group remember is a vertical column on the periodic table.

And elements in the same group, have the same number of electrons in the shell that is furthest away from the nucleus.

We call that the outer shell.

Whereas a period is the horizontal row on the periodic table.

And each period corresponds to a number of shells of electrons in an atom of that element.

Absolutely well done on those tasks.

We're now gonna talk about how properties are linked to groups of the periodic table.

So, there are two types of property that we've discussed throughout the key stage three science.

The first one being that there are physical properties.

So they describe basically the way that elements, or substances look, or the way that they behave at various different temperatures such as their melting and boiling points, their density, whether they conduct electricity, or heat and their colour, but also their chemical properties, which describe the way that they behave in chemical reactions.

Again, it's very simply just their reactivity, but whether they're acidic, or alkaline, how easy they are to burn their combustibility, or whether they can resist corrosion, or whether they're incredibly corrosive themselves.

So again, quick fire.

Which of these are examples of physical properties? I'm not gonna let you pause the video now, 'cause you should be able to read through those quite quickly.

Hopefully you've identified that all but C, are physical properties.

C is a description of a chemical property.

So again, metals, non-metals and metalloids are the three main types of elements.

Metals on the left hand side of the periodic table, they make up the vast majority of the periodic table, have typically the following properties.

They are shiny, malleable, and good conductors of heat and electricity.

They are all examples of physical properties.

Non-metals, the ones highlighted in green here, on the right hand side of the periodic table are often dull, brittle, and not very good conductors.

They're poor conductors of heat and electricity and we can often describe them as insulators.

Again, they are all examples of physical properties.

The metalloids, the section between metals and non-metals are described to be semiconductors.

They have similar properties to both metals and non-metals, but they have a very unique set of properties.

Again, that is a description of physical properties.

Quick (indistinct), which of these are examples of the physical properties of non-metals? Pause the video as you read through and press play when you're ready to hear the answer.

And the answer is A and D.

They are all examples of physical properties, but they aren't the physical properties of non-metals.

B and C are the properties of metals.

So then on the screen you can see two highlighted groups.

The first one on the left in green, that is group one.

And on the right in purple, that is group seven.

As we've already said, they have the same number of electrons.

Every element in that group have the same number of electrons on their outer most shell.

And that causes the group to have similar chemical properties.

Now we're not going to go into too much detail on how it affects it in this unit.

But later units in GCSE, you'll cover that in more detail.

But for now I think it's interesting to know that is what causes the chemical properties.

So true, or false.

Elements in the same group have similar chemical properties as they have the same number of shells of electrons.

True or false? Well the answer is false.

And here are two statements.

I'd like you to read through them both.

Pause the video as you do that and press play when you've decided which one justifies that statement being false.

Well the answer is A.

Elements in the same group actually have the same number of electrons on their outermost shell.

Elements in the same period don't really have similar chemical properties.

They show a trend in properties across the group.

Group one metals do not behave the same way as group seven halogen non-metal atoms. So here we have some diagrams showing the group one metals.

We call them the alkaline metals.

We'll learn more about that later.

And this group contains the following elements.

There are more, but the main three ones that you may have heard of are lithium, sodium, and potassium.

They have very similar chemical and physical properties.

They're very highly reactive, especially with water and they have very low melting points.

That means they melt at very low temperatures.

The group two metals, these are known as the alkaline earth metals.

Again, two that you might be familiar with.

Magnesium and calcium.

They're very similar to group one, but they do behave differently.

They aren't as reactive as group one and they have much higher melting points and densities than group one metals.

The group seven elements, again too you might be familiar with fluorine and chlorine, they are a different set of elements and they have the tendency to form salts with metals.

So, salt you might be very familiar with is sodium chloride.

That's table salt, that's made up of chlorine and sodium atoms. These elements tend to go around as diatomic molecules, so F2, CL2, BR2, but they're also very toxic.

And the central block of elements, we call the transition metals.

So these include elements like iron and copper.

These have typical properties of metals, such as being very good conductors of electricity and they are incredibly malleable.

So which of these is not a typical property, physical property specifically of transition metals? Have a read through, pause as you do so and press play when you're ready to hear the answer.

Well the answer is dull and that is the only one that is not a typical property of transition metals.

All the rest are, and they behave like most normal metals.

Which of the following statements then are true? This is some general statements then about what we've learned so far.

Pause the video as you read through and when you're ready to see the answers, press play.

Well these are the two correct statements.

The elements in the same group of the periodic table have similar chemical properties.

The periodic table doesn't only include metals and non-metals, it includes metalloids as well.

The periodic table is not organised into rows called groups.

They're called periods.

And Dmitri Mendeleev was a key role in developing the periodic table.

We move on now to some tasks.

Shown here is a periodic table with just some elements highlighted.

I'd like you to read through the passage and fill in the blanks using only the words period, or group.

Once you are ready to see the answer, press play and we'll go through it together.

Well, we can see here that elements three and four do not have similar chemical properties, because they are in the same period, not the same group.

The atomic number three, nine and 15, each increase by six every time.

The elements do not have the same chemical properties.

The periodic table does not put them in the same group.

The atomic numbers three 11 and 19 however, do increase by eight each time.

This means each element is in a different period, but they have the same, or similar, should I say, chemical properties.

The periodic table therefore puts them in the same group.

Right then, so we're gonna try and use some information we provided here to make some suggestions.

We've got two sets of elements set one of element X, Y, and Z and set two of J, K and L.

I'd like you to read through their properties and the information provided and decide which set of elements shows similarities in chemical properties and why? Pause the video as you do so and then press play when you're ready to see the answer.

So, your answer might look like set one, shows a set of elements with similar chemical properties as they all react in a similar way with iron.

Whereas set two only contains one element that reacts with iron and two elements that don't.

So we can see here that for the first set, each of them react with iron and the set two, that only element J reacts with iron, but it has to be heated.

So thank you very much for learning this lesson with me today.

Today we've covered the idea that each column of the periodic table is called a group and each row is called a period.

The periodic table was developed by a Russian scientist called Dmitri Mendeleev.

The periodic table contains all of the elements organised into groups and periods, according to their properties.

The elements in the same group of the periodic table have similar properties.

In addition to groups, elements can be divided into non-metals and metals, which includes the transition metals.

I look forward to learning with you again.

See you next time.

Bye-Bye.