Organic Chemistry and Nuclear Chemistry
This domain covers carbon compounds and nuclear change. You need the homologous series and functional groups, common organic reaction types, and balanced nuclear equations with half-life calculations.
Organic families
Carbon forms four bonds and bonds to itself, giving chains and rings. Alkanes are CₙH₂ₙ₊₂ with only single bonds (saturated); alkenes are CₙH₂ₙ with one double bond; alkynes are CₙH₂ₙ₋₂ with a triple bond. Alkenes and alkynes are unsaturated and undergo addition. Isomers share a molecular formula but differ in structure and properties. When naming, find the longest chain, number from the end nearer a branch, and name branches as alkyl groups.
Functional groups and reactions
Alcohols contain –OH, organic acids contain –COOH, esters contain –COO–, aldehydes contain –CHO, and ketones have C=O within the chain. Alkanes react by substitution with halogens; alkenes by addition of H₂, Br₂, or H₂O; hydrocarbons burn to CO₂ and H₂O. Fermentation converts glucose to ethanol and CO₂. Addition polymerization links alkene monomers without losing atoms.
Nuclear chemistry
Alpha emission (⁴₂He) lowers mass by 4 and atomic number by 2. Beta emission (⁰₋₁e) converts a neutron to a proton, so mass is unchanged and atomic number rises by 1. Positron emission lowers atomic number by 1. Gamma radiation carries energy only. Fission splits a heavy nucleus; fusion joins light nuclei. Mass and charge numbers must balance.
Worked example
²³⁸₉₂U emits an alpha particle: mass 238 − 4 = 234, atomic number 92 − 2 = 90, giving ²³⁴₉₀Th. For half-life, 80 g of a nuclide with t½ = 5 days decays for 20 days, so n = 4 and 80 × (1/2)⁴ = 5 g remain.
Traps
- Changing coefficients instead of subscripts and superscripts in nuclear equations.
- Thinking beta decay changes the mass number.
- Confusing fission with fusion.
- Naming an ester as an acid or an aldehyde as a ketone.