The transition metals (with the exception of $\mathrm{Zn}, \mathrm{Cd} \text{and} \mathrm{Hg}$) are very much hard and have low volatility. Their melting and boiling points are high.The high melting points of these metals are attributed to the involvement of greater number of electrons from $(\mathrm{n}-1)\mathrm{d}$ in addition to the $\mathrm{ns}$ electrons in the interatomic metallic bonding. In any row the melting points of these metals rise to a maximum at ${\mathrm{d}}^5$.