Why does carbon form covalent bonds? Explain tetravalency and catenation with one example each.

1. 1 · Configuration. Carbon (atomic number 6) is 2, 4: it has 4 outer electrons.
2. 2 · Why covalent. Gaining or losing 4 electrons needs too much energy, so carbon shares them.
3. 3 · Tetravalency. Carbon forms four covalent bonds, as in methane, CH₄.
4. 4 · Draw methane. Draw C in the centre with four shared pairs, one to each H, then the line structure.
5. 5 · Catenation. Carbon atoms link with each other in chains, branches and rings, as in butane, C₄H₁₀.
6. 6 · Close in one line. So carbon forms more compounds than any other element.

Scoring tip: Name both properties and give a formula for each. 'Carbon forms many compounds' alone earns no mark.