Element X has atomic number 16. Write its electronic configuration, find its period and group, say whether it is a metal or a non-metal, and write the formula of its compound with hydrogen.

1. 1 · Configuration. 16 electrons: K 2, L 8, M 6, so 2, 8, 6.
2. 2 · Period. Three shells, so period 3.
3. 3 · Group. 6 valence electrons, so group 10 + 6 = 16.
4. 4 · Nature. It needs 2 more electrons to complete its octet, so it tends to gain electrons: a non-metal (sulphur).
5. 5 · Valency and formula. Valency = 8 − 6 = 2; with hydrogen (valency 1) it forms H₂S.
6. 6 · Position sketch. Mark it in period 3, group 16, to the right of the zigzag line of metalloids.
7. 7 · Close. So the configuration alone tells an element's place and behaviour.

Scoring tip: Write the configuration first and show '10 + 6'; examiners give a mark for each step.