Why magnesium has a higher melting point than sodium?
Melting point is dependant upon packing and intermolecular forces. Magnesium and Sodium are both metals, and therefore have metallic bonding. Both are a lattice of positively charged ions surrounded by a sea of delocalized electrons. Magnesium however has 2 delocalized electrons for every one magnesium atom, it therefore forms smaller ions than Sodium, which pack more closely together. The higher number of delocalized electrons in magnesium also pull the positively charged even closer together.
