Here's why:

* Magnesium (Mg): Melting point of 650°C (1202°F)

* Lithium (Li): Melting point of 180.5°C (356.9°F)

Magnesium has a higher melting point because its atoms are held together by stronger metallic bonds. This is due to:

* Smaller atomic size: Magnesium atoms are smaller than lithium atoms, leading to a greater attraction between the positively charged nuclei and the shared electrons.

* More valence electrons: Magnesium has two valence electrons, while lithium has only one. This means magnesium can form stronger metallic bonds.