* Nonpolar molecule with two identical atoms: This suggests a diatomic molecule, like H₂ (hydrogen), N₂ (nitrogen), O₂ (oxygen), F₂ (fluorine), Cl₂ (chlorine), Br₂ (bromine), or I₂ (iodine).

* Forms ions with a 2- charge when reacting with sodium: This means element X gains two electrons to achieve a stable octet configuration.

Determining the Group:

Elements that gain two electrons to achieve a stable octet are found in Group 16 (VIA) of the periodic table. This group is also known as the chalcogens.

Example:

Oxygen (O) is a good example. It forms a diatomic molecule (O₂) and reacts with sodium to form sodium oxide (Na₂O), where oxygen has a 2- charge.

Therefore, element X belongs to Group 16 (VIA) of the periodic table.