Pearson Edexcel International GCSE Chemistry · specification 4CH1 · Paper 1 | Whole paper: Core content, all four topics · Free · no account needed
1(c) Atomic structure (4CH1 specification)
Protons, neutrons and electrons; atomic number, mass number and the isotopes that complicate the arithmetic.
Learn it on Incandio
The 2 Incandio pages that teach this — each explained in full, then proved in marked questions, taught back to an AI pupil and defended in a debate. Completely free.
- Inside the Atom — Protons, neutrons and electrons — where they are, what they weigh, what they carry, and how isotopes give an element a decimal mass.
- Electronic Configurations and the Periodic Table — Why the table has the shape it has: the group number IS the outer-shell electron count, and everything follows from that.
The teaching route this belongs to: Topic 1 · Principles of chemistry (Chemistry) — the lessons in order, with every gate.
Specification coverage
Topic 1 Principles of chemistry (c) Atomic structure — statements 1.14–1.21
Assessment objectives: AO1, AO2. Suggested learning time: 70 minutes.
Required knowledge
- The relative mass and relative charge of protons, neutrons and electrons
- Atomic number and mass number, and how to deduce the number of each particle
- Isotopes as atoms of the same element with different numbers of neutrons
- The calculation of relative atomic mass from isotopic abundances
- Electronic configurations of the first twenty elements
Required skills
- Deduce particle numbers from a nuclide symbol
- Calculate relative atomic mass as a weighted mean
- Write electronic configurations and relate them to Group number
How it is examined
- Multiple-choice and short-answer recall
- Application of the content to an unfamiliar context
- Extended open-response, marked on the quality of a connected explanation
Common mistakes
- Taking a simple average of isotope masses instead of weighting by abundance.
- Saying isotopes have different chemical properties. Chemistry is determined by electrons, which are identical — only physical properties differ.
- Confusing mass number with relative atomic mass.
This page maps the specification. The pages above teach it, and the Chemistry lessons hold the whole course — completely free.