Why is magnesium a solid at room temperature but oxygen is a gas?

Answer 1

In a metal such as magnesium, the outermost electrons come loose from their atoms, leaving behind positive ions and are shared among all the atoms in a give chunk of the metal as a common electron pool. The positively charged ions are attracted to this electron pool, so the whole mass stays together. This phenomenon is called metallic bonding. In oxygen two atoms share a set of four atoms to form a two-atom molecule that is only weakly attracted to nearby molecules, so it can move freely of other particles.

Answer 2

At room temperature, magnesium is a solid because it has metallic bonding, where positively charged metal ions are held together by a sea of delocalized electrons. This strong metallic bonding results in a solid structure. On the other hand, oxygen is a gas at room temperature because it is a diatomic molecule (O2) held together by covalent bonds. The relatively weak intermolecular forces between oxygen molecules allow them to move freely and exist as a gas at room temperature.

Answer 3

The difference in state at room temperature is primarily due to their atomic/molecular structures. Magnesium atoms are metallic, tightly packed together with strong bonding forces, resulting in a solid state. Oxygen molecules are diatomic, with weaker intermolecular forces, allowing them to move more freely and exist as a gas at room temperature.