Question

The maximum & minimum melting point of first transition and second transition series elements, respectively are obtained with:

• A. Cr & Cd
• B. Cr & Hg
• C. Mo & Cd
• D. Cr & Zn

Answer 1

The correct option is A Cr & Cd

Melting point is max. for Cr and minimum for Cd.
Electronic configuration is as follows:
$Cr=\left[Ar\right]3d^{5}4s^1$
$Cd=\left[Kr\right]4d^{10}5s^2$
Cr has 5 unpaired electrons and has strongest metallic bonding because all unpaired electron of $s$ and $p$ orbitals participate in bonding. Hence maximum melting point is obtained by$Cr$. In case of $Cd$ has no unpaired electrons not participate in bondind therefore , minimum melting point for second transition series is obtained.