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A circled plus or minus on an atom in a structure.
Also known as: Charge marking, Circled charge
A circled plus or minus on an atom gives its formal charge — a bookkeeping figure from counting electrons, not a measured charge. A formally charged atom is not necessarily where the real charge density sits, which is the distinction the notation obscures.
Marks the formal charge on an atom, calculated by counting valence electrons against those assigned in the structure.
Contexts: Laboratory
Is a bookkeeping quantity rather than a measured one, so the atom bearing a formal charge is not necessarily where the electron density is actually concentrated.
Contexts: Laboratory
A small plus or minus sign, often enclosed in a circle, placed beside an atom in a drawn structure.