Topic 2 of 8 · Form 3
Atoms, elements, compounds and bonding
Protons, neutrons and electrons; proton number and nucleon number; isotopes; electronic configuration (2, 8, 8 …). Relative atomic mass as a weighted average of isotopes.
Notes for this topic 1 file, in order
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Atomic structure
Protons, neutrons and electrons; proton number and nucleon number; isotopes; electronic configuration (2, 8, 8 …). Relative atomic mass as a weighted average of isotopes.
Ionic bonding
Electron transfer between metals and non-metals; giant ionic lattices; high melting points; conduct when molten or aqueous; dot-and-cross diagrams (e.g. NaCl, MgO).
Covalent bonding
Shared pairs of electrons; simple molecules (H₂, Cl₂, H₂O, CH₄, NH₃, CO₂, N₂ with a triple bond); low melting points; generally do not conduct.
Giant covalent structures
Diamond (hard, cutting tools), graphite (layers, conducts, lubricant), silicon(IV) oxide (high melting point, sand).
Metallic bonding
Positive ions in a sea of delocalised electrons – good conductors, malleable and ductile.
Worked example: Deduce the formula of aluminium oxide from its ions.
Al³⁺ and O²⁻ → 2 × (+3) = 3 × (2) → Al₂O₃
Check yourself
- How many neutrons are in ³⁷Cl (Z = 17)?
- Why does graphite conduct electricity but diamond does not?
- Write the formula of calcium nitrate.
Show answers
- 20
- Each carbon in graphite has one delocalised electron free to move; in diamond all four electrons are in bonds.
- Ca(NO₃)₂
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