Lesson video

- Hi, I'm Ms. Barrett from the Oak National Academy and today's lesson is Atoms, Elements and Compounds, which is the first lesson of the atomic structure and periodic table unit, the key stage four.

You're gonna find it really useful if you've got a periodic table with you today.

So if you want to pause here and make sure you've got one, that will be great.

Let's get started.

So in today's lesson, we are going to define and identify atoms, elements and compounds, and name compounds from their formula.

So here are some key words that you might have come across at key stage three and which we are learning about today.

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

An atom is the smallest unit of matter.

A compound is a substance formed by the chemical bonding of two or more elements.

So today's lesson is broken down into three parts.

Firstly, we're going to look at atoms, molecules, and elements.

Then, we're gonna have a look at compounds.

And then finally, we're gonna have a look at some chemical reactions and how we name products.

So starting with atoms, molecules and elements.

So atoms, you might have heard of these before.

These are the smallest unit of matter.

And in fact, everything in the world is made from atoms. So the screen that you are looking at right now, the clothes that you are wearing, even your body, all of these things are made from atoms. They are absolutely tiny.

So if we took some sand, and then we took just one piece of that sand, and then we zoomed in on that piece of sand and had a look, we would see it is made of lots of atoms. And then if we zoomed in even further, we would have see one atom.

Now this isn't actually possible to do because atoms are absolutely tiny.

However, this is the structure of the atom.

We're not gonna go too much into the structure today.

We're just gonna be looking at what atoms are.

So in one grain of sand, there are 43 quintillion atoms. So the number is on the screen.

I'm not gonna attempt to read that out because it is very, very long.

But you can now realise how small atoms really are, considering you can fit 43 quintillion atoms in that grain of sand, absolutely tiny.

So the only thing that is smaller than atoms are the subatomic particles that make them up.

So you might have heard of these before.

We've got protons and neutrons and electrons.

And as I said, we're not gonna talk too much about these today.

And the atomic structure that we know today is the result of many, many years of research.

And in fact, it took hundreds of years to figure out what the atom actually looks like and that's because it is so, so tiny.

So the radius of an atom, so that's from the nucleus to the outer shell, is on average 1 x 10 to the -10 metres.

So that is 0.

00000000001 metres, so really, really small.

We can't even see these under a microscope.

They are that tiny.

So atoms can be represented in different ways.

And if you search for atom on a search engine, you'll come up with all different kinds of pictures of an atom.

So these are some examples.

However, today we are going to be looking at drawing atoms as particles.

So this is what we are going to see.

So we'll have atoms that are circles of different sizes and of different colours.

So you might have also heard of molecules.

So what's the difference between an atom and a molecule? Well, if you have a look at my diagram here, can you identify which ones are atoms and which ones are molecules? So the atoms are the smallest part of an element that can exist.

So they are the single unit.

The molecules, that is defined as two or more atoms that are chemically bonded together.

And as you can see here, the two atoms can be the same type of atom, so they can be the same elements or they can be different ones.

Both of those are considered to be molecules.

So atoms can exist on their own or chemically bond with other atoms to make molecules.

So on the left-hand side here, we've got atoms, so the smallest unit of matter.

Molecules, two or more atoms chemically bonded together.

And then on the very right-hand side in this box, we've got atoms and molecules and this would be considered to be a mixture.

So let's check how much we've understood about atoms so far.

Which diagram shows atoms only? Have a little look, A, B, or C? Have you got it? The correct answer is C.

So you can see here that the atoms are single units.

They are just one particle, so that is an atom.

Which diagram shows molecules only? Okay, so that one is A.

So all of those particles, they are all in twos or in pairs, so all of those are molecules.

Okay different pictures this time.

So it's not the same as before, so look very carefully.

Which diagram shows two molecules and three atoms? I'll give you a second to work that out.

Have you got it? That one is B.

So there you can see two molecules.

We've got a green molecule and a red molecule.

And also we've got one green atom and two red atom.

Right, so we're gonna talk about elements now.

On the left, these are elements.

So we have a grey solid and we have the black particles which are a gas.

These are both elements.

On the right, these diagrams are not elements.

So what do you think defines an element? Well, an element is a substance made from one type of atom.

So if you have a look at the difference between these two pictures, on the left-hand side, those diagrams have one type of atom.

They're all the same colour.

On the right-hand side, both of those diagrams, the liquid and the solid, both have two different types of atoms present.

So those are not considered to be an element.

So if we took a copper pipe and we zoomed in as far as we possibly could, we would be able to see that it's made from copper atoms and it's a solid, so they are arranged in an irregular arrangement.

On the right-hand side here, we've got a piece of carbon or charcoal.

And if we zoomed on on this one, we would see that it's just made from carbon atoms. So copper and carbon are both considered to be elements because they're both made from one type of atom only.

So elements, substances made from one type of atom and the number of protons in the nucleus determines the element.

So this is the atomic number that you can see on the periodic table.

So on the right-hand side here, we've got the atomic symbol for oxygen and its atomic number, the smaller number, is eight, so that means oxygen has eight protons.

Each element is represented by a one or two-letter chemical symbol.

So you can see here oxygen's is O.

There are 118 elements that are currently known to exist.

There might be more.

We just haven't discovered them yet.

And these are all displayed in this.

What is this? Well, this is the periodic table.

So you can see here all of the elements with their one or two-letter representation and it shows the atomic number and the atomic mass as well.

We're gonna go into this more in a different lesson.

So elements can be solids, liquids, or gases.

So you can see the particle diagrams for solids, liquids, and gases here.

So some examples at room temperature, iron is a solid.

So all metals, most metals, there is mercury that is not solid, but the rest of them are solid at room temperature.

Bromine, bromine is a liquid and oxygen is a gas.

All of those are elements from the periodic table.

So some are solid, some are liquids and some are gases.

So let's check how much we know about atoms and elements.

An element is a substance made of two or more types of atom.

Have a think.

Is that true or is that false? And don't forget to justify your answer.

So that one is false and that's because an element is a substance that's made from one type of atom, not two or any more than that.

It has to be one type of atom.

Which of the following diagrams shows an element? So have a look very carefully.

Have you got it? C is the one that shows the element.

Why was that? Well, if you have a look at the diagrams, that is the only one where there is one colour or one size.

So that is one type of atom.

So that must be the element.

Which element has the symbol Co? Now you might need your periodic table here, so do grab that if you haven't got it already.

Is it copper, carbon, cobalt or calcium? So that one is cobalt.

Now there's a lot that begin with C.

So it's really important that we don't get them muddled up and we do check that periodic table to make sure we're using the right one.

Cobalt is Co.

Which determines the element? Is it the number of electrons, the number of neutrons, or the number of protons? So the element is determined by the number of protons.

Okay so onto your first task of the lesson.

So what you're going to do, there are three boxes on your sheet, and I want you to draw a particle diagram to match the term listed underneath.

So the first box says atoms of two different elements.

The second says three elements that are molecules.

And the last one says a molecule composed of three elements.

So think really carefully, especially with those second and third ones to make sure you get those the right way round.

Good luck, pause the video, and come back once you've completed it.

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

Now remember that these are just examples.

Yours might look slightly different but as long as you've got the right numbers, the types of atoms, then we are good.

So have a look.

On the left-hand side, you've got atoms of two different elements.

So I've drawn them as I've got three atoms and coloured them in black and I've got two that are white.

But what's important here is not the number but it's the fact that they are all single units and you've got two different colours, all size is present.

In the middle box, I've got three elements that are molecules.

So again, it doesn't matter on the number, but each one of those three needs to have two or more atoms and they have to be the same colour for each of the molecules because they are elements.

If you've drawn a molecule that's got one black and one white circle, that's not an element because then there are different types of atoms. On the last one, a molecule composed of three elements.

So you need to just draw one molecule here and needs to have three circles and each of those needs to look different.

So you might have drawn those different sizes, you might have drawn those different colours.

But as long as there are three different types of atom, then you are good.

Really well done, let's move on to the next part.

So next you're gonna use your product table to complete these tables.

So here are some elements and their names, but they don't have the symbols.

Ad some have the symbols but not the element name.

So go away, use your periodic table, pause the video and come back once you're finished.

Right, let's go through the answers.

So calcium, the symbol is Ca.

Li, that's lithium.

Magnesium, Mg, C, carbon.

Beryllium is Be, potassium, K.

So a bit of a strange one there, it doesn't match.

It's not a P, you would expect it to be P, but P is phosphorous.

Al, aluminium, fluorine, F, Cl, chlorine and neon, Ne.

Give those a tick if you've got those right.

Really well done for finishing your first task.

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

So in our next part, we are gonna be looking at compounds.

So on the left here, these are two diagrams of some compounds.

On the right, these are not compounds.

So what's the difference here? What do you think defines a compound? Is it a substance that contains two or more elements? Because on the right, they've just got one type of atom or one element.

And on the left, these have got two.

So is that what defines a compound? Well, yes partially, but there is more to it.

So on the left here, this is a compound.

And on the right, this is a mixture and is not a compound.

So what else do we need to add to our definition? What's the difference here? Well, a compound is a substance formed by the chemical bonding of two or more elements.

So there are two or more elements, but they need to be bonded together.

So when elements react, they can form compounds.

So here we've got carbon reacting with an oxygen molecule.

These are elements and that forms carbon dioxide and carbon dioxide is a compound.

It's difficult to separate compounds back into the original elements and that's when you know it might be a compound as 'cause they can only be separated through a chemical reaction.

So if we wanted to get the carbon and oxygen back from carbon dioxide, you would have to do a chemical reaction like this.

So carbon dioxide would've to react to form carbon and oxygen.

So we need to put energy into that reaction to make it happen.

So that is very, very difficult to do.

Whereas mixtures, they can be separated really easily.

For example, sand and water, you could filter it to get rid of the sand from the water.

That wouldn't require a chemical reaction.

So a chemical compound, to add to our definition, it contains elements in fixed proportions.

So this, do you recognise this? This is H2O and that's water.

This on the right-hand side is H2O2 and this is not water and is in fact hydrogen peroxide and that would be very, very dangerous and toxic if you drunk that.

So would definitely not recommend drinking H2O2.

It's really important that when we are done talking about compounds, we're making sure that the elements are in the right proportions.

So all compounds are molecules but not all molecules are compounds.

So H2O is a molecule because it's got two or more atoms but it's also a compound because those two atoms or two more atoms are different.

We've got oxygens and we've got hydrogens and they're chemically bonded together.

This on the right-hand side is hydrogen, so H2, and it's a molecule but it's not a compound because those two atoms are exactly the same.

Sodium reacts with chlorine gas to produce sodium chloride.

So here's sodium that reacts to chlorine and that forms sodium chloride.

Now how would you describe sodium and chlorine? Well, I would describe sodium as a metal.

It's grey, it's a solid, whereas chlorine is a gas.

And in fact, it's a yellow-green gas and it is a non-metal.

So if you were to react these two together to make sodium chloride, what would you expect the properties of sodium chloride to be? Would it be a mixture of the two? Would it be a yellow-green gaseous metal? Well in fact, sodium chloride is table salt.

So this is something you've probably come across and you might have even put on your chips and it looks like this.

So sodium chloride is a non-metal and it's white and it is a crystalline solid.

So it looks really different to the elements that it started from.

So the properties of compounds are different from the properties of the elements that they're made from.

All right, let's see how much we've understood.

True or false? The substance shown is a compound.

So on the right-hand side, you'll see a diagram.

Is that a compound? That is a compound, that is true, and that is because it is composed of two or more different elements that are chemically bonded together.

Next one, it is easy to turn a compound back into the original elements.

Can you remember what I said about this? This one is false and that's because energy is required to break the bonds between the elements.

So it is not easy to break those chemical bonds in that compound.

Iron sulphide will have similar properties to iron and sulphur.

Is that true or false? So that one is also false because compounds have different properties to the elements that they are made from.

Okay so we'll move on to the second task.

So in this task, I've got six different diagrams and you are going to label each image using two of the keywords below.

So for example, something could be a compound and also a molecule or it could be an atom and also element.

So pause a video here, have a go.

And then, we'll go through the answers once you're finished.

All right, let's go through the answers.

So that was a little bit tricky.

That was a lot to think about there, so don't worry if you found that difficult.

Let's go through the first one.

So the first one here, each molecule, oh, I'm giving you an answer.

So each one, each substance has one white atom and two black atoms. So what do we call that? Well, like I said, that is a molecule but it's also a compound because there's two different atoms there.

The second one, this is an atom and an element.

Every single one of those particles, those atoms are separated.

There's no chemical bonding there.

So that must be an atom.

And there are also elements, and in fact, there's two elements there.

There's the white element and there's the black element, so two different types.

Number three, this one is a molecule and also an element, only one type of atom.

Number four, this is a molecule and a compound.

So just like number one, it's just a little bit bigger but that doesn't matter 'cause remember the definitions are two or more.

Number five, you've got a solid of white particles.

This is a molecule 'cause there's more than one atom but it is an element because all those atoms are the same.

And then number six, these are molecules and compounds.

Some are made of two atoms, some are three, but they're still molecules and compounds 'cause there's two different atoms chemically bonded together.

So from your diagrams, which boxes show mixtures.

And then, you're going to explain why those diagrams you selected are mixture.

So pause the video and answer those two questions.

Okay so the mixtures were two and six and that's because there's two different substances there that are not chemically bonded together.

So number two, there was a white element and there was the black element but they're not chemically bonded.

And the number six, there were two different molecules made from the same elements but some had two atoms, some of them had three.

So that was a mixture.

Really well done on task two.

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

So our final section of the lesson is chemical reactions and naming products.

So chemical reactions involve rearranging atoms by breaking and making of chemical bonds.

So here I've got this reaction.

Do you recognise it? This is hydrogen reacting with oxygen to form water.

Now I've drawn you the particles here, two atoms of hydrogen and one, sorry, two molecules of hydrogen and one molecule of oxygen.

And we need to break the bonds between those molecules so that we have just all those single atoms. And then those atoms will rearrange and they will form new bonds, make new chemical bonds in a different way.

And that's what chemical reactions are, the making and breaking of chemical bonds to rearrange those atoms. So for chemical reactions, we use equations to represent the process.

So we can have this, reactant + reactant gives us product and we can use word equations.

For example, iron + sulphur gives us iron sulphide or we can use symbol equations using the chemical symbols such as Fe + S gives us FeS.

So similar equations need to be balanced.

They must have the same number of atoms of each element on both sides of the equation.

So here, how many atoms of calcium are there? How many atoms of sulphur are there? So on both the left and the right-hand side in the reactants and the products, there are one atom of calcium and one of sulphur.

So therefore, that equation is balanced and we need to check for that when we are writing chemical equations.

Beware that some molecules are diatomic and this means that they hang around in pairs and they never exist as single atoms and there's quite a few.

So we've got hydrogen, oxygen, nitrogen, fluorine, chlorine, bromine and iodine, and the bottom four are all of group 7 or all in group 7.

So make sure you watch out for that when you're balancing equations because you can't then write just an H, it's got to be an H2.

So let's put our chemical reactions knowledge to the test.

Lithium carbonate reacts with hydrochloric acid to produce lithium chloride, water and carbon dioxide.

What are the reactants? Write them down.

So the reactants are lithium carbonate and hydrochloric acid.

That's what you start with.

They are the reactants.

So same reaction, what are the products? So the products are what we end with.

So that is a lithium chloride + water, and carbon dioxide, well done.

Magnesium reacts with oxygen to produce magnesium oxide.

What is the word equation? Write it down.

Okay the word equation is magnesium + oxygen gives magnesium oxide.

Well done if you've got that one, we're gonna make it a little bit harder.

Magnesium, chemical symbol Mg, react to oxygen, O2, to produce magnesium oxide, MgO.

What is the balanced symbol equation? Now remember oxygen's diatomic.

You can't just write O.

It has to be O2.

Pause the video and have a go at balancing that equation.

So do you think you've got it? The balanced symbol equation is 2 Mg + O2 makes 2 MgO.

We've gotta make sure the number of atoms are the same on both sides.

Really well done if you've got that.

So compounds are produced from the reaction between elements.

All compounds have a name and a formula.

So for example, we've got water.

Its formula is H2O.

And sodium chloride, its formula is NaCl and 'cause that's cause it's made from sodium and chlorine.

So most compounds have a two-word name and there are three rules we need to follow.

Firstly, the element furthest to the left on the periodic table comes first in the name.

So for example, this is calcium oxide in this diagram, not oxide calcium.

The second rule, if the compound is made from two elements, then the name ends in -ide.

So here, as I said before, it's calcium oxide, not calcium oxygen.

Sometimes, prefixes are used to determine how many atoms of each element are present in the compound.

So here we've got carbon monoxide on the left and here we've got carbon dioxide on the right.

So we use these prefixes, mon-, di-, tri-, tetra-, penta-, hexa- to indicate how many we've got sometimes, particularly when we are talking about oxygen.

So the last rule is when compounds are made of three different atoms and one is oxygen, the name ends in -ate.

So if it's sodium carbonate, that means it's made from sodium, carbon and oxygen.

If it's potassium sulphate, that it's made from potassium, sulphur and oxygen.

Lithium nitrate, that is made from lithium, nitrogen and oxygen.

So what do you think calcium sulphate is made from? Well, that is made from calcium, sulphur and oxygen.

Okay so a compound contains magnesium and oxygen.

What is the name of this compound? The name is magnesium oxide.

Well done if you got it.

A compound contains beryllium, nitrogen and oxygen.

What is the name of this compound? So remember when there are three atoms present and one is oxygen, the name changes a little bit.

This is beryllium nitrate, not beryllium nitrogen oxide, beryllium nitrate.

Well done if you got it.

Carbon trioxide is composed of: one carbon and three oxygen atoms; three carbons and three oxygens; or three carbons and one oxygen atom.

So that is one carbon and three oxygen atoms because the tri is connected to the oxide bit.

So it means three oxygen atoms. Really well done if you've got those right.

So a chemical formula uses chemical symbols to show the elements present in a compound and the number of atoms of each element that are in that compound.

So like we have before, carbon monoxide, this is CO.

Carbon dioxide, this is CO2 because the 2 shows us that there are two oxygens.

So there are rules for the formulas as well that we need to follow.

The rule number one is the same as the previous for the naming.

The element that is furthest to the left of the periodic table is always written first.

So this is Li-F not F-Li.

Number two, when there are more than one atom of the same element present, we use subscript numbers as these little numbers after the corresponding element.

So here, this is H2O, not H with a big 2O, the 2 has to be little.

And here, this is H2, not 2H or the little 2 being on the left-hand side, it's gotta be after the corresponding element.

Rule three, if there is a multiple of a polyatomic ion, so this means an ion that contains many atoms, within the compound, then brackets are used.

So for example, calcium hydroxide has two hydroxide ions and this hydroxide ion is a polyatomic.

It contains more than one atom.

And in this sticks together as a pair, the oxygen hydrogen don't split up.

So this is calcium, so Ca.

And then, we've got the OH with brackets with a little 2.

Because it's got two hydroxide ions, we put the brackets around both the oxygen and the hydrogen.

So let's see what we've understood about formulas.

Give the formula for the compound that contains one iron atom, one carbon atom and three oxygen atoms. Do you think you've got it? This is FeCO3.

So that's the formula.

There's three oxygens, one of everything else.

The formula for the compound that contains two aluminium atoms and three oxygen atoms. Well, that one is a Al2O3, so make sure that those numbers are little and written after the corresponding element.

Give the formula for the compound that contains one iron atom and three hydroxide ions.

So this one would be Fe with the OH in brackets, and then a little 3.

Well done if you got those 'cause these can be a little bit tricky.

Okay let's move on to task three for the lesson.

Give the word and balanced simple equations for the following reactions.

So have a read of those, come up with the word and a symbol equation and make sure you balance them.

Pause the video and come back once you're finished.

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

So calcium reacting with chlorine to make calcium chloride, we have calcium + chlorine gives calcium chloride and the symbol equation Ca + Cl2 gives us CaCl2.

Now remember those formulas were written in the question.

This one, we've got the right number of atoms on both sides, it's already balanced.

Potassium reacts with sulphur to produce potassium sulphide.

Potassium + sulphur gives potassium sulphide.

And then, this would be 2 K + S gives K2S.

Because there's two K's on the right, we have to make sure there are two on the left.

And the last one, iron reacting with oxygen to produce iron oxide, we've got iron + oxygen gives iron oxide.

And 4 Fe + 3 O2 gives 2 Fe2O3.

Now that was quite a hard one to balance.

So if you got that, really well done.

Right, so part B, you need to complete the table.

You've got a list of atoms present.

You just need to give the name and formula and there's an example shown there to help you.

Pause the video, have a go and good luck.

Okay let's go through the answers.

So the one potassium, one fluorine, was potassium fluoride and that was KF.

One calcium and two iodine is calcium iodide and that's CaI2.

And I'll show you the rest so you can check them.

So hopefully, you remembered when you've got two oxygens, we put dioxide.

And on the last one because there was three atoms and one was oxygen, that changes to sulphate.

Really well done if you got those right.

So that is the end of the lesson.

Really well done for your hard work during this lesson.

Let's summarise what we've learned today.

Atoms are the smallest unit of matter.

Elements are substances made from one type of atom.

When two or more atoms bond together, a molecule is formed.

If the two or more atoms bonded are different elements, this is a compound.

If two or more atoms are not chemically bonded, this is a mixture.

Chemical reactions involve the rearranging of atoms by breaking and making chemical bonds.

These can be displayed using word or symbol equations.

Compounds have names and formulas.

Fantastic work today, really big well done.

And give yourself a massive pat on the back.

You've made it to the end of the lesson.

Thank you so much for watching and thank you for using the Oak National Academy and I'll see you next time.