Element of 3d series with highest melting point is

The correct answer is Option (1) → Cr

Transition metals have high melting points because, besides the ns electrons, electrons of the (n−1)d subshell also take part in metallic bonding. The more unpaired d electrons available, the stronger the interatomic bonding. So in each series the melting points rise to a maximum at d⁵ and then fall as the d electrons pair up; manganese is an exception with an unusually low value.

Writing the configurations of the given metals:

• Cr (Z = 24): [Ar]3d⁵4s¹ — 6 unpaired electrons, all available for bonding.

• Mn (Z = 25): [Ar]3d⁵4s² — the stable half-filled 3d⁵ with a paired 4s² holds its electrons tightly; Mn has an anomalously low melting point.

• Fe (Z = 26): [Ar]3d⁶4s² — 4 unpaired electrons.

• Co (Z = 27): [Ar]3d⁷4s² — 3 unpaired electrons.

So among the given elements, chromium, with the largest number of unpaired electrons taking part in metallic bonding, has the highest melting point.

NCERT (2026-27 edition):
Physical Properties – …