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EdPlace's Key Stage 3 Home Learning Science Lesson: Atoms, Elements and Compounds

Looking for short lessons to keep your child engaged and learning? Our experienced team of teachers have created English, maths and science lessons for the home, so your child can learn no matter where they are.  And, as all activities are self-marked, you really can encourage your child to be an independent learner.  

Get them started on the lesson below and then jump into our teacher-created activities to practice what they've learnt. We've recommended five to ensure they feel secure in their knowledge - 5-a-day helps keeps the learning loss at bay (or so we think!)

Are they keen to start practising straight away? Head to the bottom of the page to find the activities. 


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Now...onto the lesson!


Key Stage 3 Statutory Requirements for Science
Key Stage 3 students should understand the differences between atoms, elements and compounds and the chemical symbols and formulae for elements and compounds.



Atoms, Elements and Compounds

You may have heard of atoms before, but what've they got to do with elements and compounds

Firstly, atoms are the basic building blocks of all matter on Earth and they're very tiny (far too small to be seen with the naked eye). Substances can be categorised as either elements or compounds. Both of these are made up of atoms, the only difference is an element is made of one type of atom whereas compounds are made of two or more different types of atoms.

This topic is abstract and can be difficult for students to understand as atoms are far too small for them to see. So, it's a good idea for you both to spend some time looking at the diagrams in this article to help them visualise this concept better. 

We're confident that if you follow the step-by-step guide below your child will be able to:

1) Identify elements and compounds shown in diagrams

2) Recognise elements and compounds from their formula

3) Explain the difference between elements and compounds


Step 1: Understand the Key Definitions

There are four keywords and definitions to get to grips within this topic.  Once your child has got this, they'll find this topic much easier.

An atom is the smallest particle that can exist. Everything is made from atoms. Atoms are shown in diagrams as small circles.

An element is made up of one type of atom only. For example, a piece of pure copper is made up of only of copper atoms. There are 118 known elements on Earth and they are all listed in the periodic table. 

A compound is a substance made up of two or more atoms of different elements chemically joined (or bonded) together. For example, carbon dioxide gas (CO2) consists of one carbon atom and two oxygen atoms bonded together. 

A molecule describes two or more atoms bonded together (all compounds are molecules and some elements are too). 

The atoms of some elements, like Neon, do not join together and instead exist on their own as individual atoms (they are not molecules). The atoms of other elements, however, like Hydrogen join together as pairs, making a molecule.


Step 2: Diagrams of Different Substances

Imagine you are presented with diagrams of different substances? It's very easy to become bogged down with these keywords but only two need to be applied to each diagram. A good rule to remember is to decide first whether a substance is an atom or a molecule. Then decide whether the substance is an element or a compound.

Atoms of the same element in diagrams will be drawn as the same size and they will be the same colour (as shown in diagram 2).

If the atoms are of different elements they will be a different colour or size (as shown in diagram 3).


Step 3: Symbols

Elements and compounds are not always displayed as diagrams. Symbols are used to represent elements and each element from the periodic table has a symbol. This symbol can be made up of one or two letters but it always starts with a capital letter. For example, the symbol for nitrogen is N and the symbol for lithium is Li. 

A formula is a shorthand way of showing the elements in a compound.  The formula for sodium chloride is NaCl. This compound must be made up of two elements as there are two capital letters present in the formula. By consulting the periodic table you can discover that this compound is made up of one sodium atom (Na) and one chlorine atom (Cl). Another compound, potassium oxide has the formula K2O. It consists of two potassium atoms (symbol K) and one oxygen atom (symbol O).

Your child needs to ensure they take extra care when writing down the symbols of elements in the periodic table, paying close attention to whether the letters should be in upper or lower case. 

For example, writing CO instead of Co completely changes the substance in question. CO is the formula for the compound carbon monoxide (a deadly, colourless gas), whereas Co is the symbol for the element Cobalt (a magnetic metal found in the Earth’s crust).


Step 4: Identify the Difference Between Elements and Compounds

Try these questions together to see if you can identify the differences between elements and compounds: 

1) What substance is made from only one type of atom? An element or a compound?

2) Look at the following diagrams and state whether the substance is firstly an atom or a molecule and state if it is an element or a compound:






3) Are the following elements or compounds?

a) C

b) CuO

c) NaF

d) Ne

e) H2O

f) He


Step 5 - Activity Time!

Now, you’ve covered this together why not put this to the test and assign your child the following activities in this order. All activities are created by teachers and automatically marked.

Plus, with an EdPlace subscription, we can automatically progress your child at a level that's right for them. Sending you progress reports along the way so you can track and measure progress, together - brilliant!

Activity 1 - Compounds

Activity 2 - Mixtures

Activity 3 - Atoms, Elements, Compounds and Mixtures

Activity 4 - Define Atoms, Elements, Compounds and Mixtures

Activity 5 - The Development of the Periodic Table

(Activities 3, 4 and 5 are GCSE level for extra stretch and challenge.)



1) Element

2a) Molecule, compound

b) Atom, element

c) Molecule, element

d) Molecule, compound

e) Molecule, element

3a) Element

b) Compound

c) Compound

d) Element

e) Compound

f) Element


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