Question

Nitrogen is a gas at room temperature while phosphorous is a solid .Explain

Answer 1

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The size of nitrogen is quite small. As a result two nitrogen atoms can be linked to each other by three covalent bonds in order to complete the octets of both the nitrogen atoms. This diatomic molecule N2 is very stable and has very negligible attraction towards other diatomic nitrogen molecules. Thus there is weak interaction between nitrogen molecules. So nitrogen exist as gas.

While phosphorus being large in size has less tendency to form three bonds. Therefore, P atoms completes octets by sharing its valence electrons with three other P atoms. As a result, it exist as tetratomic P4 molecule. In white phosphorous there is network which holds the phosphorous atoms together. This catenation tendency of phosphorus is reason why it exist as solid.

Answer 2

Answer:

N2 is exist as diatomic molecule in which two nitrogen atoms are attached to each other by triple bond this triple bond is due to p(pie)-p(pie) multiple bonding (sidewise overlapping) and such bonding is not possible in phosphorus due to it's large size but possible in nitrogen due to it's small size. 

In case of phosphorus four atoms are associated so it have high molecular mass ,large magnitude of venderwall forces so phosphorus is solid and nitrogen is