The Nitrogen Group
Nitrogen is the most important element in Group V of the Periodic Table. Diatomic nitrogen is the principal constituent of the air. When bonded to hydrogen in the form of ammonia, nitrogen is an essential plant nutrient. Certain plants called legumes and certain bluegreen algae are able to transform nitrogen into ammonia in a process called nitrogen fixation. Ammonia based fertilizers are widely used in agriculture.
Phosphorous, another Group V element, is also used as a fertilizer. With oxygen, it forms phosphates used in fertilizers. Calcium phosphates are the major constituents of bones and teeth.