名词

1. 氮;氮气
Nitrogen is a colourless element that has no smell and is usually found as a gas. It forms about 78% of the earth's atmosphere, and is found in all living things.

1. a common nonmetallic element that is normally a colorless odorless tasteless inert diatomic gas
constitutes 78 percent of the atmosphere by volume
a constituent of all living tissues

Synonym: Natomic number 7