Which of the following 3d series metals has the highest melting point?

The correct answer is Option (1) → Cr

Transition metals have high melting points because (n−1)d electrons as well as ns electrons take part in metallic bonding. Across the 3d series the melting point rises to a maximum at d⁵ and then falls, with manganese as an exception.

• Cr (3d⁵4s¹) — the d⁵ metal: the highest of the four.

• Mn (3d⁵4s²) — an anomalously low value, well below Cr.

• Fe (3d⁶4s²) — past the d⁵ maximum, so lower than Cr.

• Zn (3d¹⁰4s²) — no 3d electrons take part in its metallic bonding; it is not even a hard metal, and has the lowest melting point here.

NCERT (2026-27 edition):
4.3.1 Physical Properties – “The transition metals (with the exception of Zn, Cd and Hg) are very hard and have low volatility. Their melting and boiling points are high. Fig. 4.1 depicts the melting points of transition metals belonging to 3d, 4d and 5d series. The high melting points of these metals are attributed to the involvement of greater number of electrons from (n-1)d in addition to the ns electrons in the interatomic metallic bonding. In any row the melting points of these metals rise to a maximum at d⁵ except for anomalous values of Mn and Tc and fall regularly as the atomic number increases.”

Fig. 4.1: Trends in melting points of transition elements