Determine which ions have noble-gas configurations. Check all that apply. Zr4+ S2− Part A Select the atoms whose ions have an electron configuration of nd6 (n = 3, 4, 5 …). For example, the 2+ ion for V ends the electron configuration with 3d 3. Check all that apply. Co Pt Ru. Part A
Electron configuration Simple 2.8.8… rule. Not realising that the s, p, d configuration is an amplification of the 2.8.8… format. Deducing group number for the p-block elements (e.g. group7 – not counting the s-electrons with the p-electrons as outer electrons). Misunderstanding electron configuration for ions.