Capstone: Position predicts properties
One idea ties the whole periodic table together: an element's position (its group) is set by its electronic structure, and that decides how it behaves. Sort each element into the family its outer shell puts it in.
Drag each element into a box — or tap it to step through the boxes. Then press Check.
Group 11 outer electron
Group 77 outer electrons
Group 0full outer shell
Transition metalsmiddle block
✅ C1 Atomic Structure and the Periodic Table — Quick-Reference Summary
- Atom = smallest part of an element. Element = one type of atom. Compound = 2+ elements bonded.
- Proton (+1, mass 1) and neutron (0, mass 1) are in the nucleus. Electron (−1, negligible mass) is in shells.
- Atomic number = protons = electrons (neutral atom). Mass number = protons + neutrons.
- Isotopes = same protons, different neutrons. Same chemistry. Different physical properties.
- Ar = weighted average mass of all isotopes (considering abundance), and you can calculate it from isotope masses and abundances.
- Shells fill inwards → outwards: max 2 in 1st shell, max 8 in 2nd and 3rd shells.
- Group = outer electrons. Period = number of shells. Noble gases (Group 0) have full outer shells → very unreactive.
- Atom radius ≈ 0.1 nm (10⁻¹⁰ m). Nucleus is ~1/10,000 of atom but contains almost all the mass.
- Early tables used atomic mass — Newlands (Law of Octaves, 1864) criticised for mixing metals/non-metals and leaving no gaps. Mendeleev (1869) left gaps and predicted undiscovered elements — accepted when predictions proved correct.
- Modern table ordered by atomic number (not mass) — isotopes explain why mass ordering occasionally fails.
- Group 1 alkali metals: low density, soft. React with oxygen → metal oxide; with chlorine → metal chloride; with water → metal hydroxide + H₂. Reactivity increases down the group (outer electron further from nucleus, more easily lost). Noble gases (Group 0): full outer shells → inert. Boiling points increase with increasing relative atomic mass down the group.
- Group 7 halogens: diatomic molecules, halide ions (−1). Reactivity decreases down the group (harder to gain electron). Melting/boiling points increase. More reactive halogen displaces less reactive from solution.
- Transition metals: high m.p., high density, hard, form coloured compounds, variable ion charges, act as catalysts (Fe: Haber; Pt: nitric acid; Ni: hydrogenation). T
That is the foundation for the whole of Paper 1: every reaction in the topics that follow is really about what these atoms do with their outer electrons. Next is C2 — Bonding, Structure & the Properties of Matter, where those electron arrangements decide how atoms bond and what the resulting substances are like.