Last revised by Daniel J Bell on 11 May 2023

Nitrogen (chemical symbol N) is one of the basic organic elements and is a key constituent of amino acids, the building blocks of proteins, and of nucleic acids (i.e. DNA and RNA). On earth it is the most abundant element found in its pure form and comprises 78% of all breathable air

Nitrogen (N2) is a colourless odorless diatomic gas with an atomic number 7 and atomic weight 14.007. It has a melting point of -210°C and a boiling point of -196°C 1. Nitrogen is characteristically inert, and its diatomic molecule has the strongest covalent bonds found in nature between two atoms of the same element.

The stable isotope nitrogen-14 accounts for more than 99.6% nitrogen found on earth. A tiny amount of nitrogen-15 makes up the remainder of the naturally-occurring nitrogen 2. Many other nitrogen isotopes (all mass numbers sequentially from N-10 to N-25) have been observed experimentally, all with half-lives less than one hour 2.

Nitrogen per se is not poisonous. However in an atmosphere of pure nitrogen, death will obviously rapidly ensue as no oxygen is available.

Although not due to an inherent toxicity of the element, nitrogen gas plays a key role in the pathogenesis of decompression illness.

Daniel Rutherford (1749-1819), a Scottish scientist published his discovery of nitrogen in his PhD thesis in 1772 1,5

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