WCH11 Structure, Bonding and Introduction to Organic Chemistry

Lessons in WCH11

1. Amount of substance: the mole
   n = m / M; n = c x V (V in dm³); use the balanced equation's mole ratio.
2. Balanced, ionic and test-tube equations
   Balance atoms and charges; include state symbols; in ionic equations cancel spectator ions and keep the species that change.
3. Empirical and molecular formulae
   Mass to moles, divide by the smallest, make whole numbers; molecular formula = (Mr / empirical mass) x empirical formula.
4. Reacting masses, yield and atom economy
   n = m/M, use the mole ratio, m = n x M. Yield compares actual with theoretical; atom economy compares useful product with all reactants.
5. Gas volumes and the ideal gas equation
   n = V/24.0 at r.t.p.; pV = nRT with p in Pa, V in m³ and T in K.
6. Concentration, dilution and parts per million
   c = n/V; g/dm³ = mol/dm³ x M; c1V1 = c2V2; ppm = (part / whole) x 10⁶.
7. Atoms, isotopes and mass spectrometry
   Isotopes: same protons, different neutrons. Ar = weighted mean of isotopic masses. Cl2 peaks 70 : 72 : 74 in ratio 9 : 6 : 1.
8. Ionisation energies and electron shells
   IE rises with nuclear charge and falls with distance and shielding. A big jump in successive IEs marks a new shell; dips at Groups 13 and 16 show sub-shells.
9. Orbitals and electron configurations
   Fill 1s 2s 2p 3s 3p 4s 3d 4p; single occupancy before pairing; Cr and Cu take 4s1; groups share outer configurations.
10. Periodicity: trends across Periods 2 and 3
    Across Period 3 melting point rises to Si (metallic then giant covalent), then falls for simple molecules. First IE rises across a period and falls down a group
11. Ionic bonding and ionic radii
    Ionic bond: electrostatic attraction between oppositely charged ions in a lattice. Smaller, more charged ions bond more strongly. Isoelectronic ions shrink as n
12. Covalent and dative bonding
    Covalent bond: attraction of two nuclei to a shared pair. Dative bond: both electrons from one atom (NH4+, Al2Cl6). More shared pairs, shorter and stronger bond
13. Shapes of molecules and ions
    Pairs repel to be as far apart as possible; lone pairs repel more and reduce angles by about 2.5° each.
14. Electronegativity, polarity and polarisation
    Electronegativity: attraction for a bonding pair. Polar bonds in a symmetrical molecule can cancel. Small, highly charged cations polarise large anions, adding
15. Metallic bonding and giant structures
    Metallic bond: attraction between positive ions and delocalised electrons. Diamond: 4 bonds, hard, non-conductor. Graphite and graphene: 3 bonds, delocalised el
16. Naming organic compounds and structural isomers
    Homologous series: same functional group, differ by CH2. Name from the longest chain with lowest locants. Structural isomers: same molecular formula, different
17. Alkanes as fuels: cracking, reforming and pollution
    Cracking: long alkanes to shorter alkanes plus alkenes. Reforming: straight to branched or cyclic. Pollutants: CO, NOx, SO2, soot, unburned hydrocarbons.
18. Combustion and free-radical substitution
    Homolytic fission gives radicals. Free-radical substitution: initiation (UV), propagation (radical in, radical out), termination (two radicals join). It gives m
19. Alkenes: bonding and E/Z isomerism
    C=C is one σ bond and one π bond. No rotation about C=C gives E/Z isomers when each carbon has two different groups. Z = higher priorities together, E = opposit
20. Addition reactions of alkenes
    Alkenes: H2/Ni, X2, HX, steam/H3PO4, KMnO4 to a diol. Bromine water turns colourless. Electrophilic addition goes via the most stable carbocation.
21. Addition polymers and their disposal
    Addition polymers form when C=C opens; repeat unit = the two C=C carbons with a single bond. Waste: recycle, incinerate with gas removal, or use biodegradable p

Next exams for WCH11

• January 2027: Mon 11 Jan 2027, morning, 1h 30m
• Summer 2027: Wed 5 May 2027, afternoon, 1h 30m

From Pearson's final timetables. All exam dates. Always confirm your entries with your exams officer.