# Why is the melting point of magnesium anomalous? [duplicate]

The melting and boiling points for the Group II elements are as follows: $$\begin{array}{ccc} \text{Element} & \text{Melting point / }\mathrm{^\circ C} \\ \hline \ce{Be} & 1289 \\ \ce{Mg} & 650 \\ \ce{Ca} & 842 \\ \ce{Sr} & 769 \\ \ce{Ba} & 729 \end{array}$$ (source: Greenwood & Earnshaw, Chemistry of the Elements 2nd ed., p 112)

As you can see, the overall trend is decreasing, but magnesium is an exception. Just like the alkali metals, melting point should decrease for the heavier elements of the group because of the weaker bonding. Why is magnesium different?

The other trends for this group, such as density, atomic radius, and first ionization energy follow the expected pattern with no exceptions.