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2. Atoms, molecules and stoichiometry

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  1. 2.1 Relative masses of atoms and molecules

    1. 2.1.1Unified atomic mass unit

      • Define the unified atomic mass unit as one twelfth of the mass of a carbon-12 atom

    2. 2.1.2Atomic mass, Ar, isotopic mass

      • Define relative atomic mass, Ar, relative isotopic mass, relative molecular mass and relative formula mass, both referred to as Mr, in terms of the unified atomic mass unit

  2. 2.2 The mole and the Avogadro constant

    1. 2.2.1

      • Define/use: mole in terms of the Avogadro constant

  3. 2.3 Formulas

    1. 2.3.1Ionic formulas and oxidation numbers

      • Write ionic formulas from ionic charges and oxidation numbers. - Predict ionic charge from Periodic Table position - Recall ions: NO3-, CO3^2-, SO4^2-, OH-, NH4+, Zn2+, Ag+, HCO3-, PO4^3-

    2. 2.3.2Balanced and ionic equations

      • Write balanced equations and ionic equations without spectator ions; use appropriate state symbols.

    3. 2.3.3Terms: empirical and molecular formula

      • Define/use: empirical and molecular formula

    4. 2.3.4Terms: anhydrous, hydrated and water

      • Use terms: anhydrous, hydrated and water of crystallisation

    5. 2.3.5Empirical and molecular formulas

      • Calculate empirical and molecular formulas, using given data

  4. 2.4 Reacting masses and volumes (of solutions and gases)

    1. 2.4.1

      • Perform calculations including use of the mole concept, involving: - (a) reacting masses (from formulas and equations) including percentage yield calculations - (b) volumes of gases (e.g. in the burning of hydrocarbons) - (c) volumes and concentrations of solutions - (d) limiting reagent and excess reagent (When performing calculations, candidates’ answers should reflect the number of significant figures - given or asked for in the question. When rounding up or down, candidates should ensure that significant figures are neither lost unnecessarily nor used beyond what is justified (see also Mathematical requirements section).) - (e) deduce stoichiometric relationships from calculations such as those in 2.4.1(a)–(d)