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Regarding the d-block (transition) metals, which one of the following statements is INCORRECT?

1. Compounds containing ions of transition elements are generally coloured
2. Among the 3d-series elements, zinc has the lowest melting point
3. They display variable oxidation states that always differ from one another by exactly two units
4. They readily form complex compounds

Correct answer: They display variable oxidation states that always differ from one another by exactly two units

Solution

Transition metals show variable oxidation states that typically differ by ONE unit (e.g. Fe2+/Fe3+, Mn shows +2,+3,+4,+6,+7), not by two units only. Differences of two units are characteristic of many p-block elements (inert pair effect). The other three statements are correct: partially filled d-orbitals allow d-d transitions giving colour; Zn (3d10 4s2, no unpaired d-electrons / no d-bonding) has the lowest melting point in the 3d series; and small, highly charged ions with vacant d-orbitals readily form complexes.

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