Why water is a liquid and hydrogen sulphide is a gas?

Explanation

Oxygen forms a stable diatomic molecule. In oxygen molecule, two atoms of oxygen are joined together through double bond (O = O). The multiple bonding in the oxygen is possible due to small size of oxygen. Due to smaller molecular mass oxygen is a gas at room temperature.
Sulphur, selenium and tellurium have polyatmoic molecules because multiple bonding is not possible in these elements due to large atomic size. For example, sulphur has 8 atoms arranged in the form of a puckered ring per molecule `(S_8)`. In this sturcture, each sulphur atom is linked to two other sulphur atoms through single covalent bonds. Consequently, shlphur has high molecular mass. Because of this, sulphur is a solid at room temperature.