GCSE · Chemistry · AQA · Spec 8462
Size and mass of atoms; isotopes
How small is an atom?
Read the scale from the nucleus out to a familiar one-metre length.
Nucleus radius
about 1 × 10⁻¹⁴ m
The nucleus is less than 1/10 000 of the atom's radius, so it occupies an extraordinarily small central scale.
Relationship matrix
Tap any cell to reveal it. Tap a column header to read one property down every item.
Each cell hides a short answer and the reason behind it. Predict before you tap.
Read the symbol, find the particles
Use a generic atom written as ²³₁₁X.
- Read the top-leftThe mass number is 23, meaning there are 23 protons and neutrons altogether.
- Complete the atomFor this neutral atom, the electron count matches the proton count, so it has 11 electrons.
Spot the isotopes
Compare what stays the same and what changes.
Two atoms of element X are written as ²⁰₈X and ²²₈X. Which statement is correct?
WHAT YOU'VE LEARNED
A quick recap of today's lesson.
Zoom from the tiny atom to its nucleus, then use particle counts to understand mass number and isotopes.
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