1 Reading the notation

Redox notation packs a lot into small symbols. Every one below appears on this page.

📖 Symbols used in oxidation–reduction

8 terms

Cover the right column and check you can say what each one means.

Oxidation number: A bookkeeping charge assigned to an atom, written with the sign first: +7, −2. It is not a real charge. It is a way of tracking electrons. Distinguish from an ionic charge, written sign LAST: Na⁺, SO₄²⁻.
E° (standard electrode potential): The voltage of a half-cell measured against the standard hydrogen electrode, under standard conditions. The ° means standard conditions. A more positive E° means the species is more readily REDUCED.
E°_cell: The overall cell voltage: E°(cathode) − E°(anode). Positive means the reaction is spontaneous. E° is intensive. Never multiply it when you scale a half-equation.
OIL RIG: Mnemonic: Oxidation Is Loss (of electrons), Reduction Is Gain.
Anode / cathode: Anode = where oxidation happens. Cathode = where reduction happens. True in BOTH galvanic and electrolytic cells. Only the SIGNS flip: the anode is negative in a galvanic cell, positive in electrolysis.
| and || (cell diagrams): A single bar is a phase boundary (metal | its solution). A double bar is the salt bridge separating the two half-cells.
(s) (l) (g) (aq): State symbols: solid, liquid, gas, aqueous (dissolved in water). Required in full equations.
e⁻: An electron. In a half-equation, electrons on the LEFT means reduction (gain); on the RIGHT means oxidation (loss).

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Sign first or sign last?

Oxidation number writes the sign FIRST (+2, −1). Ionic charge writes it LAST (Ca²⁺, Cl⁻). If you see “+2” it is an oxidation number; “2+” is a charge.

Practice for this standard covers the whole topic — flashcards and quiz.