Question

Dinitrogen is a gas but phosphorus is solid

Answer 1

N has small size so form multiple bond and behave as small molecule existing in gaseous state.but P is bigger in size as well existing as P4 become larger molecule existing in solid state.

Answer 2

Hey !!

Nitrogen due to small size and high electronegativity forms pπ - pπ multiple bonds and exist as a diatomic molecule. These molecules are held together by waek van der Waal forces and hence N₂ exist as a gas at room temperature. In constrast due to larger size and lower electronegativity P does not form pπ - pπ bond with itself rather it prefer to form single P-P bonds and exist as tetrahedral P₄ molecules. Due to bigger size, the force of attraction holding P₄ molecules are quite stronger and cannot broken by the collision of molecules at room temperature and hence solid at room temperature.

Hope it helps you !!