Why is nitrogen a gas while phosphorus is solid ?

Explanation

Nitrogen atom because of small size can form multiple bonds, `N -= N` . These `N_2` molecules are held together by weak van der Waals. forces of attraction,

` therefore ` it has a low b.pt. and is gas at room temperature. P because of large size forms single bonds, exist as `P_4` molecules. These `P_4` molecules have large sizes and there are large van der Waals. forces of attraction, hence it is solid at room temperature.