The increasing order of the melting points of following transition metals is
(A) Fe
(B) Mn
(C) Cr
(D) V
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (B), (A), (D), (C)
Transition metals have high melting points because, besides the ns electrons, electrons from the (n−1)d orbitals take part in metallic bonding. The more unpaired d electrons available, the stronger the bonding. Across a row the melting points therefore rise to a maximum at d5 and then fall, with manganese anomalously low.
The configurations follow from the atomic numbers:
(D) V (Z = 23): \( \mathrm{[Ar]\,3d^{3}\,4s^{2}} \), three unpaired 3d electrons.
(C) Cr (Z = 24): \( \mathrm{[Ar]\,3d^{5}\,4s^{1}} \), five unpaired 3d electrons and one 4s electron, the d5 maximum of the row.
(B) Mn (Z = 25): \( \mathrm{[Ar]\,3d^{5}\,4s^{2}} \); the stable half-filled 3d set holds its electrons tightly, so they take little part in bonding and the melting point is anomalously low.
(A) Fe (Z = 26): \( \mathrm{[Ar]\,3d^{6}\,4s^{2}} \), past the maximum, so lower than V and Cr but above Mn.
\( \displaystyle \ce{Mn} \lt \ce{Fe} \lt \ce{V} \lt \ce{Cr} \)
NCERT (2026-27 edition):
Physical Properties – …
