Atoms have a nucleus made up of protons and neutrons
Protons are positively charged particles.
Neutrons have no charge.
The Mass number is the sum of protons and neutrons

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Electrons orbit the nucleus
They are negatively charged particles.
For atoms, the number of protons equals the number of electrons, which equals the atomic number

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The atomic number is the top number. It tells you how many protons and electrons the element has.
Atomic No. = Protons = Electrons
The bottom number is the mass number.
It tells you what the number of protons and neutrons add up to

​Mass No. = protons + neutrons
Sodium: 11 protons, 11 electrons
How many neutrons does sodium have?

Postman Pat Electrons

Electrons occupy specific shells or orbitals
Each orbital can manage only a certain number of electrons (we explain why in Stage 6 Chemistry)
The first shell can only handle a maximum of 2
The second shell, a maximum of 8
The third shell, a maximum of 8
That's where we stop in Year 8!

Li: ATOMIC NUMBER 3, therefore 3 electrons:

C: ATOMIC NUMBER 6, therefore 6 electrons:

Cl: ATOMIC NUMBER 17, therefore 17 electrons:

Ne: ATOMIC NUMBER 10, therefore 10 electrons: