Lesson video

Welcome to today's lesson on atoms, elements and compounds.

It's part of the unit "Atomic structure and the periodic table." My name's Mrs. Mytum-Smithson and today we're going to look at atoms, elements and compounds.

Sometimes this can be a little bit confusing, but we're going to go through this bit by bit and look at lots of different examples.

By the end of this lesson, you should feel much more confident about the difference between an atom, element, and compound.

By the end of today's lesson, you should be able to describe elements being made up of only one type of atom and that elements can combine chemically to form compounds.

Here are some keywords for today's lesson.

They are atom, element, compound, chemical formula, chemical composition.

On the next slide, there's some sentences that include these keywords, so if you want to read those, pause the video, read the sentences, and then press play when you're ready to start the lesson.

This lesson consists of two learning cycles, atoms and elements, and compounds.

Our first learning cycle is atoms and elements, so let's get learning.

And atom is the smallest particle of a substance.

All of the 118 known elements are listed on the periodic table.

Elements are made up of one type of atom.

If it's not on the periodic table, if you can't find the name of it, then it's not an element.

A quick check for understanding.

A list of all known elements is found on the element table, the periodic table or the chemical table.

Pause the video for some thinking time.

Press play when you've got your answer.

Well done if you said a list of all known elements is found on the periodic table, well done if you got that one correct.

Some elements are monoatomic.

These consists of only single atoms. Here's our monoatomic atom.

For example, helium.

Here's a picture of it.

You can see it consists of one atom.

Diatomic, so diatomic atoms consist of two of the same type chemically bonded together.

This is called a molecule.

So dia comes from the word meaning two, compared to mon which means one.

Atomic means from the atom.

So we've got here, we've got, this is a diatomic atom, this is oxygen.

You can see that there are two oxygen atoms chemically bonded together.

That's what that overlap shows, so the overlap shows that they are chemically bonded together.

A quick check for understanding.

Which image or images represent a diatomic molecule in an element? Pause the video now for some thinking time and press play when you've got your answer.

Well done if you said A.

A represents a diatomic molecule because there are two of them, so two atoms chemically joined together, and they are the same type of atom.

So if you have a look at B, B is a monoatomic atom, so that is just one atom.

And C, because they are two different atoms, that means that it's not an element.

So although it's a diatomic molecule, it's not an element.

So well done if you said A.

Atoms of all elements consist of a nucleus in the centre of the atom that contains protons and neutrons.

There you go, you can see those are labelled up there for you.

And shells that have got electrons orbiting around the nucleus so that electrons move around the nucleus.

A quick check for understanding now.

True or false, all elements are made up of the same subatomic particles.

Is that true or is that false? Pause the video for some thinking time, press play when you've got your answer.

Well done if you said that that was true, all elements are made up of the same subatomic particles, and here's a justification.

Atoms are made up of three subatomic particles called protons, electrons, and neutrons.

Or B, atoms are made up of two subatomic particles called protons and neutrons.

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

Well done if you said A, atoms are made up of three subatomic particles called protons, electrons, and neutrons.

Remember, subatomic just means that these particles are smaller than an atom.

Well done if you got that one correct.

Quick check for understanding.

True or false, diatomic elements are always made up of the same number and type of atoms. Is that true or is that false? Pause the video for some thinking time and press play when you've got your answer.

Well done if you said that that was true.

Diatomic elements are always made up of the same number and type of atoms. We want a justification for that.

Diatomic elements are always made up of two of the same type of atom, or diatomic elements are sometimes made up of two different types of atom.

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

Well done if you said A, diatomic elements are always made up of two of the same type of atom, so there must be two of them and they must be the same type to be an element.

Well done if you've got that correct.

All elements consist of their own atoms with a unique number of protons defining the element.

Let's have a look at an example, so here's beryllium.

Beryllium has four protons and you can see that there because that is the atomic number which tells you the number of protons.

No other element has got four protons in it.

The number of protons is unique to each element.

So if it did have four protons, it would always be beryllium.

Let's a look at nitrogen.

You can see that nitrogen's got an atomic number of seven.

That means that nitrogen has got seven protons.

No other element has got seven protons, only nitrogen.

A quick check for understanding now.

True or false, the number of protons can vary in elements.

For example, an atom of oxygen can have eight or more protons.

Is that true or is that false? Pause the video for some thinking time, press play when you've got your answer.

Well done if you said that that was false.

Let's have a look at a justification now.

Each element has a unique number of protons, or there can be an element with the same number of protons as another element.

Pause the video.

When you've got your answer, press play, and I'll tell you if you're right or not.

Well done if you said A, each element has got a unique number of protons.

I've got part one of Task A for you now.

Find the number of protons for the following elements.

You will need a periodic table to do this.

So we've got helium, sodium, potassium, iron, and gallium.

And then we've got the symbols here, Co, Te, I, Y, and W.

Pause the video while you complete the task and press play and we'll go through the answers together.

Well done for completing that task, I hope you found it quite quick to do.

So, helium has got 2 protons.

Sodium's got 11 protons.

Potassium's got 19 protons.

Iron's got 26 protons.

Gallium's got 31 protons.

Then we did some symbols.

So this is cobalt, this is element number 27, so it's got 27 protons.

We've got tellurium that's got 52 protons.

Iodine's got 53 protons.

Yttrium's got 39 protons.

And tungsten's got 74 protons.

So well done if you've got all of those correct, you're doing really well.

Here's part two and three of Task A.

Here's what I want you to do.

For part two, I want you to find the element name for the number of protons.

So using your periodic table, look up the number of protons and then write down the element name.

So that's 12 protons, 25 protons, 28 protons, 49 protons and 86 protons.

Then part three, find the element symbol, so this time you're writing the chemical symbol for the number of protons.

So that's 6 protons, 13 protons, 55 protons and 82 protons.

And finally, 80 protons.

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

Well done for completing parts two and three of Task A.

Here's what you needed to do.

So on your periodic table you needed to look for the number of protons.

So the number of protons is simply the atomic number, which is the smaller of the two numbers on your periodic table.

So first we're going to look up 12 protons and we're gonna find that that is magnesium.

25 is manganese.

28 is nickel.

49 is indium.

86 is radon.

Now we're onto part three of Task A, find the element symbols this time, so this time we're just writing, we are looking up the atomic number which tells us the number of protons and all we're going to do now is write the symbol.

So, 6 protons, that would be carbon.

13 protons, aluminium.

55 protons is cesium, Cs, so that's a capital C and a lowercase S.

82 protons, that's lead, so that's a capital P and a lowercase B.

80 protons, that's mercury, so that's a capital H and a lowercase G.

Well done for completing all of those, I hope you got 'em all right.

Well done for working hard and completing the first learning cycle, atoms and elements.

Now we're going to move on to learning about compounds.

Everything around us is made of different combinations of atoms, either on their own or in compound form.

So here's a bedroom here.

Maybe this one looks a little bit like yours, perhaps not.

And here we've got a wardrobe that's made of atoms. We've got the window that's made of atoms, so the glass in the window and the window frame is made of atoms. The paint painting the walls is made of atoms. The bedding, so the pillow and the bed, they're made of atoms. The chair and the floor.

Everything in that room and surrounding us is made of atoms. So this dog here sat on a beach.

So the beach, the sand, the sea, the pebbles, they're all made of atoms, even the dog and the dog's collar and the dog tag, they're all made of atoms too.

And then we've got a pizza.

The pizza base, the cheese, the tomato, the herbs on the top, the plate it's sitting on, the air that's surrounding that pizza, they're all made of atoms either on their own or in compound form.

So everything in these pictures are made of atoms. I've got a quick check for understanding for you now.

Which image or images are made of atoms? So take a look at the pictures, pause the video, choose your answer, and then press play and we'll go through it.

Well done if you said A, B, and C are made of atoms. So everything around us is made of atoms, all food, all animals, all substances, they're all made of atoms. Well done if you've got all three correct.

Compounds are made from two or more different elements chemically bonded together.

So here's an example of a compound, here's ammonia.

You can see that we've got one nitrogen atom and surrounding it are three hydrogen atoms and they are chemically bonded together.

We show that they're chemically bonded by having an overlap.

So this is an example of a compound ammonia.

Then we've got carbon dioxide.

Carbon dioxide is made up of carbon, so a carbon atom, and then it's got two other atoms, oxygen, chemically bonded to it.

So you can see that that is chemically bonded by the overlap.

So here's some examples which are not compounds.

So this, although you've got two atoms and although they're chemically bonded together, because they're made of the same atom, the same type of atoms, that is an element, not a compound.

So here we've got two different elements, but you can see that they are separate.

Because they are separate, they're not chemically bonded.

So that is also not a compound.

So we've got two compounds there, ammonia and carbon dioxide, and then we've got two examples which are not compounds.

A quick check from under standing.

Select the image or images which represent compounds.

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

So well done if you said B and C.

B and C represent compounds because they consist of two or more different types of atoms chemically bonded together.

A is not a compound because although there are two atoms and although they are chemically bonded, they are the same type of atom, which means that A would represent an element and not a compound.

Well done if you've got those two correct.

Globally, scientists use the same element symbols to share chemical compositions.

Here's some antique bottles that have been used for chemicals.

Although we can read the words, they probably don't mean very much to us because some of them are in a different language.

And this makes sure if we use the symbols it makes sure that despite different languages and chemical names, the chemical formula are the same everywhere in the world.

For example, hydrogen chloride is called chlorwasserstoff in German, but has a formula HCl that everyone can understand.

This also makes it much easier to write if we write a chemical formula using element symbols.

A quick check for understanding for you now.

Scientists communicate using the written name of a compound.

Is that true or is that false? Pause the video now and then press play when you've got your answer.

Well done if you said that that was false.

Now I want you to justify your answer.

Is it, A, scientists use a chemical formula for compounds? Or is it B, all scientists speak English, so they use a English name for compounds? Pause the video for some thinking time, press play when you've got your answer.

Well done if you said scientists use a chemical formula for compounds.

Not all scientists speak English and so they would be writing the name of them in lots of different languages.

It's much easier for scientists to be able to communicate across the world if they have the same chemical formula to read.

We can write the formula for a compound if we know what elements make up the compound.

So here this compound consists of one sulphur atom bonded to two hydrogen atoms. That bonding is shown by the overlap.

It's called hydrogen sulphide and the formula for this is H2S.

The two here, the subscript 2, shows that the number of that type of atoms. So because there's two hydrogens, we write a subscript 2 next to the hydrogen.

Some examples of compound formula are ammonia.

This is made up of one nitrogen atom you can see in the centre with the N, and three hydrogen atoms, so the formula for this is NH3.

If there's only one of an atom, we leave off the one because we assume that if there's no number next to it, there's just a one, so we don't write it.

So NH3 for ammonia.

This is carbon dioxide here, so it's got one carbon atom, two oxygen atoms, so the formula for this is CO2.

Here's a quick check for understanding.

When writing the formula of a compound, the numbers should be, should they be superscript, which is smaller and above the element symbol? The same size as a chemical symbols? Or should they be subscript which is smaller and below the element symbol? Pause the video, select your answer, and press play and I'll tell you if you're right or not.

Well done if you said that they were subscript.

So they need to be smaller and below the element symbol.

A quick check for understanding now.

Propane has three carbon atoms and eight hydrogen atoms in the molecule.

What is the formula for propane? So here's a picture of the molecule of propane.

What's its formula? Is it C8H3? C3H8? C3H8? C3H8? I want you to pay attention to the size of the numbers and where they are.

Pause the video, choose which one you think is correct, and then press play and I'll tell you if you're right.

Well done if you said that it was C3H8.

So there's three carbons, eight hydrogens, and we need to write those numbers smaller and below the line in subscript.

Well done if you got that correct.

To write a compounds formula, you need to know the symbols of the atoms in the compound, know how many of each type of atom there are.

So here's an example.

This is nitrogen dioxide and you can see the formula for this is NO2.

So we've got one nitrogen atom.

Remember, we don't write the number one.

And then following that we've got two oxygens, so we're going to write those in subscript, so that's smaller and below the element symbol.

I'd like you now to write the formula for the two compounds pictured.

Pause the video, write the formula for these two compounds, then press play and we'll go through the answer.

Well done for completing that.

The formula for the first one is HCl, so that should be a capital H, capital C, lowercase L.

No numbers there because there's just one of each atom.

The bottom one, the formula for this one is CH4.

There's one carbon and four hydrogens, so we write capital C for the carbon, capital H for the hydrogen, and we've got four of them so we must write that number four smaller and lower than the symbols.

Well done if you've got those two correct.

A quick check for understanding now.

Select the formula or formulae which represents the compound or the compounds.

So which one of these represents compounds? So you can choose one or more of them.

Pause the video whilst you do that, and then press play and we'll go through the answers.

Well done if you said H2SO4 and NaCl.

So A is not a compound because there are the same type of atom there.

Although there are two of them, they're the same type.

And C, there's only one type of atom there, so that means that that is an element also.

Well done if you've got those two correct.

I've got a task for you now, so here's part one of Task B.

Sort the chemicals into compounds and elements.

Use a periodic table to help you.

So I've got two lists.

Here's a list in words.

Iron, copper sulphate, hydrogen fluoride, mercury, argon, sodium, sodium chloride, potassium iodide.

And then I've got some in symbols.

So I'll take a look at those symbols.

H2S, O2, W, Xe, Cl2, LiF, NaBr, MgO.

Sort 'em into two lists so you'll have a list of compounds and a list of elements, and you can use a periodic table to help you.

Pause the video whilst you complete that task, press play and we'll go through the answers.

Well done for completing that task.

Hopefully you've got two columns now, one labelled compounds, another labelled elements.

So first one we're going to do is iron and then copper sulphate.

Essentially, if it appears on the periodic table, it's an element.

If not, then it's going to be a compound.

So copper sulphate.

Hydrogen fluoride is also a compound.

Then we've got three elements, mercury, argon, sodium, they're made up of one type of atom.

And then we've got sodium chloride, potassium iodide, you can see that they are made up of two different types of atoms chemically bonded together.

Got H2S, got O2.

Hope you didn't get caught out with that one.

Although there's two of them, because they're the same type of atom, it means that it's an element.

W, Xe, they're elements.

Cl2, again, like O2, there's two of them but because they're the same element, it means that it's an element and it's not a compound.

And then the rest of them, LiF, NaBr, MgO, you can see from those that there are two elements, different elements chemically joined together.

Well done if you've got all those correct.

Here's part two of Task B.

What I'd like you to do now is write the formula for the following compounds.

So we've got a picture the following compounds and all I want you to do is write the formula for them.

So pause the video, write the chemical formula for them, and then press play and we'll go through the answers together.

Well done for working hard and completing this task.

Let's go through the answers.

We've got HBr.

You might have written this, BrH, that's technically still correct.

We've got H2O.

If you've written this OH2, then that's fine.

Your numbers, remember, must be subscript, so they must be smaller and lower than the element symbol, otherwise you've not got it correct.

Here we've got PCl3.

We've then got CO2.

C2H6, so you may have written this H6C2.

Providing that they're little numbers, so the subscript numbers are next to the correct element, then I'll still give you the mark.

And finally, this one, it looks a bit complicated, but it's really just a question of counting.

So two carbons, four hydrogens in total, and two oxygens.

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

Now I've got the final part of Task B.

Explain why scientists would use a chemical formula rather than a chemical name.

So pause the video, answer the question, then press play and we'll go through the answer together.

Well done for completing that task.

Let's go through the answer now.

So explain why scientists would use a chemical formula rather than the chemical's name.

So your answer could include these ideas.

So you don't need to get the correct answer word for word, but you need to include the key ideas of to overcome language barriers, so different scientists who speak different languages can all understand chemical formula.

It's easier or it's quicker to write, or easier or quicker to communicate.

It shows that the chemical composition or what elements the chemical is made from.

So well done if you've got those ideas down.

Here's a summary for today's lesson.

Atoms of every element consist of the same three subatomic particles.

Protons, electrons, and neutrons.

All elements consist of their own atoms with a unique number of protons defining the element.

Everything around us is made of different combinations of atoms, either on their own or in compound form.

We use element symbols in formulae as a common language to share chemical compositions.

Well done for working hard throughout the lesson and completing all of those tasks.

I hope you feel more confident now about telling the difference between an atom, an element and a compound, and also that you're able to write chemical formulae for simple compounds.

Well done for working really hard.