Explain why atoms have no overall electrical charge, despite containing charged particles.

Edexcel GCSE Chemistry (1CH0) — 1.3 Atomic structure · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

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

Model answer (4 marks)

Protons carry a positive charge, electrons a negative charge and neutrons are neutral.

In a neutral atom the number of protons equals the number of electrons.

Because the positive and negative charges are equal in magnitude, they cancel each other out.

Therefore the atom has no overall electrical charge.

Examiner tips

Use the exact terms ‘proton’, ‘electron’, ‘neutron’, ‘positive charge’, ‘negative charge’, ‘neutral’
Show the equality of protons and electrons and explain the cancellation
Keep the answer concise – 4 marks only
Avoid unnecessary words such as ‘in this essay’

Common mistakes

Confusing the charge of neutrons with that of protons
Failing to state that the numbers of protons and electrons are equal
Using vague language like ‘balance’ without explaining the cancellation

Mark scheme (4 marks)

Protons have a positive charge (and electrons have a negative charge)
Neutrons have no charge / are neutral
The number of protons equals the number of electrons
The positive and negative charges cancel out / balance, giving no overall charge

Key terms in this question

electrical charge · atom