# In first transition series, the melting point of Mn is low because

$\begin{array}{1 1}(a)\;\text{Due to }d^1\text{ configuration, metallic bonds are strong}\\(b)\;\text{Due to }d^5\text{ configuration, metallic bonds are weak}\\(c)\;\text{Due to }d^7\text{ configuration, metallic bonds are weak }\\(d)\;\text{None of these}\end{array}$

Due to $d^5$ configuration, metallic bonds are weak. $d^5$ orbital is half filled as a result 3d electrons are more tightly held by the nucleus and this reduces the de-localization of electrons resulting in weaker metallic bonding.
Hence (b) is the correct answer.
answered Jan 30, 2014