Chemical element notation

The notation of the 118 known chemical elements is prescribed by the International Union of Pure and Applied Chemistry (IUPAC) ¹. 

Each chemical element has a long name and a symbol. In English the long name is only capitalized as part of title or sentence case. Chemical element names are not proper nouns and therefore are otherwise always in lowercase.

Symbols are either one or two letters (e.g. F, Xe, U etc.):

• the initial letter is always capitalized
• if there is a second letter it is always in lowercase

Correct usages:

• Carbon's atomic number is 6 which means it has 6 protons in each of its atoms.
• The fluorine atom used in PET imaging is a radioisotope with a mass number of 18.

See also

• isotope notation
• sulfur vs sulphur