Chemical symbol definition

A chemical symbol is the standardized abbreviated representation of an element. Many symbols have one or two letters, with the first uppercase and the second lowercase when present. Capitalization is part of the meaning.

Meaning and context

C represents carbon, O oxygen, and Na sodium. Some symbols reflect names from another language or historical usage rather than the first letters of the current English name. A symbol identifies the element, not a particular isotope or sample amount by itself.

Examples and usage

Co is cobalt, while CO is a formula containing carbon and oxygen. That difference shows why changing letter case can change the interpretation substantially. A formula combines symbols with additional notation to represent a chemical species or composition.

What to check

Use the periodic table to confirm an unfamiliar symbol. Do not invent a personal abbreviation for an element in an equation. Charges, subscripts, and isotope labels add information beyond the basic element symbol and should be read separately.

Explore more: Chemistry and Elements