Contents
Return after a break
What can you recall?
describe
Recall and explain
Keep the lesson closed. (a) Define the proton number (atomic number) and the mass number (nucleon number). (b) A sodium atom has proton number 11 and mass number 23. Describe its structure: where each kind of particle is, how many there are, and the relative charge and relative mass of each. (c) State which single change to the atom would turn it into a different element.
describe: give the features or what happens.
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Scope and sources
Cambridge IGCSE Chemistry 0620 · 2026–2028 v2 · Original learning materials.
Atomic structure (2.2 Core 1–6): protons, neutrons and electrons with their relative charges and masses, proton number and mass number, the electronic configuration of the first 20 elements and their ions, the full outer shell of the noble gases, and how outer-shell electrons and occupied shells match the group and the period. Isotopes and relative atomic mass, ionic bonding and the trends of the Periodic Table are left to their own modules.
Apparatus, amounts and times in the experiment are illustrative. Real practical work follows a teacher-approved safety method.
Official Cambridge syllabus