(a) Why do transition elements show variable oxidation states?
(i) Name the element showing maximum number of oxidation states among the first series of transition metals from Sc (Z = 21) to Zn (Z = 30).
(ii) Name the element which shows only + 3 oxidation state.
(b) What is lanthanoid contraction? Name an important alloy which contains some of the lanthanoid metals.

Explanation

### Step-by-Step Solution

#### (a) Why do transition elements show variable oxidation states?

1. **Understanding Variable Oxidation States**:
Transition elements exhibit variable oxidation states primarily due to the small energy difference between their d-orbitals and the outermost s-orbitals. This allows both sets of orbitals to participate in bonding, leading to the formation of different oxidation states.

**Explanation**:
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