Nitrogen is a chemical element with symbol N and atomic number 7. At room temperature, it is a gas of diatomic molecules and is colourless and odorless. Nitrogen is a common element in the universe, estimated at about seventh in total abundance in our galaxy and the Solar System.
As a modified atmosphere, pure or mixed with carbon dioxide, to preserve the freshness of packaged or bulk foods (by delaying rancidity and other forms of oxidative damage). Pure nitrogen as food additive is labelled in the European Union with the E number E941.
Nitrogen can be used as a replacement, or in combination with, carbon dioxide to pressurise kegs of some beers, particularly stouts and British ales, due to the smaller bubbles it produces, which makes the dispensed beer smoother and headier. A pressure-sensitive nitrogen capsule known commonly as a "widget" allows nitrogen-charged beers to be packaged in cans and bottles.