Question

Explain the variation in melting points of the transition elements.

Answer 1

1. All transition elements are metals and the strength of metallic bonding increases as the number of unpaired electrons increases.

2. In transition elements as atomic number increases, the number of unpaired electrons increases from (n – 1)d¹ to (n – 1)d⁵.

For example in 3d-series, 

melting points increase from ₂₁Sc to ₂₄Cr in 4d-series from ₃₉Y to ₄₂Mo, and in 5d-series from ₇₂Hf to ₇₄W.

3. After (n – l)d⁵ electronic configuration, the electrons start pairing, hence the number of unpaired electrons decrease, hence metallic character, melting points decrease from (n-1)d⁶ to (n – 1)d¹⁰.

4. In all transition series the melting point increases steadily up to d⁵ configuration and after this melting point decreases regularly.