In chemistry, a formal charge (FC) on an atom in a molecule is defined as: Chemistry (derived from the Arabic word kimia, alchemy, where al is Arabic for the) is the science that deals with the properties of organic and inorganic substances and their interactions with other organic and inorganic substances. ... Properties An atom (Greek άτομον from ά: non and τομον: divisible) is a submicroscopic structure found in all ordinary matter. ... A molecule is the smallest particle of a pure chemical substance that still retains its chemical composition and properties. ...

FC = number of valence electrons of the atom - number of Lone pair electrons on this atom - half the total number of electrons participating in covalent bonds with this atom. In chemistry, valance electrons are the electrons located within the outermost energy level of an atom. ... A lone pair is an electron pair without bonding or sharing with other atoms. ... Covalently bonded hydrogen and carbon in a molecule of methane. ...

When determining the correct Lewis structure (or predominant resonance structure) for a molecule, the structure is chosen such that the formal charge on each of the atoms is minimized. It has been suggested that Lewis dot diagram be merged into this article or section. ... Resonance structures are diagrammatic tools in organic chemistry to symbolize resonant bonds between atoms in molecules. ...

Examples:

• carbon in methane

FC = 4 - 0 - 8/2 = 0

• Nitrogen in NO₂^-

FC = 5 - 2 - 6/2 = 0

• double bonded oxygen in NO₂^-

FC = 6 - 4 - 4/2 = 0

• single bonded oxygen in NO₂^-

FC = 6 - 6 - 2/2 = -1