2. How can a gas at room temperature (like oxygen) become solid?

The physical state of the material depends on the intermolecular interaction between hydrogen moleculesand here this is only a fairly weak dispersion force, which is reasonable because the molecule is certainly non-polar, and is not many electron. ... Dihydrogen, dinitrogen, and dioxygen are ALL room temperature gases

Explanation: Several of the nonmetals are gases in their elemental form. Elemental hydrogen (H, element 1), nitrogen (N, element 7), oxygen (O, element 8), fluorine (F, element 9), and chlorine (Cl, element 17) are all gases at room temperature, and are found as diatomic molecules (H2, N2, O2, F2, Cl2).