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Atomic Size and Mass

AQA GCSE Chemistry (8462) — Atomic structure and the periodic table

What You Need to Know

Recall the approximate radius of an atom (0.1 nm) and its nucleus.
Recall the relative masses of protons (1), neutrons (1), and electrons (very small).
Define mass number as the sum of protons and neutrons.
Define isotopes as atoms of the same element with different numbers of neutrons.
Calculate the number of protons, neutrons, and electrons in an atom or ion given atomic and mass numbers.