UPSC Combined Geo-Scientist, Mains · 2024 · Mains Paper I

Q11(c)(ii). Coordination numbers of first-row metals

5 marks
Topic: Chemistry of d- and f-block elements
Answered

Question

(ii) Why are high coordination numbers not usual for first row d-block elements?

Answer in brief

The relatively small first-row metal ions provide less space for many ligands; coordination numbers 4 and 6 are generally more favourable than 8 or 9.

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Topic notes: transition elements: 3d, 4d and 5d compared, atomic radii and the lanthanide contraction, oxidation states and oxidising power, with every Civil Services, IFoS and Geo-Scientist PYQ →

Coverscoordination numberfirst row transition metalssteric crowdingionic size3d vs 4d 5d

All parts of Question 11

11(a) Calcium in powdered milk10 marks
11(b) High oxidation states in the first d series10 marks
11(c)(i) Why HfO₂ is denser than ZrO₂5 marks
11(c)(ii) Coordination numbers of first-row metals5 marks