Common Polyatomic Ions

Ammonium cation

$NH_4^+$, formed when ammonia gains a proton.

Hydronium cation

$H_3O^+$, formed when water gains a proton.

Hydroxide anion

$OH^-$ , a negatively charged ion formed when a hydroxyl group loses a proton.

Acetate anion

C₂H₃O₂⁻ , a negatively charged ion formed from acetic acid when it loses a proton.

Cyanide anion

$CN^-$ , a negatively charged ion formed from hydrogen cyanide when it loses a proton.

Peroxide anion

$O_2^{2-}$, a negatively charged ion consisting of two oxygen atoms bonded together, commonly found in compounds like hydrogen peroxide.

Carbonate anion

$CO_3^{2-}$ , a negatively charged ion composed of one carbon atom and three oxygen atoms, often found in rocks and minerals.

Nitrate anion

$NO_3^{-}$ , a negatively charged ion consisting of one nitrogen atom and three oxygen atoms, commonly found in fertilizers and explosives.

Phosphate anion

PO₄³⁻

Sulfate anion

SO₄²⁻

Chlorate anion

ClO₃⁻

Bromate anion

BrO₃⁻

Iodate anion

IO₃⁻

chromate anion

CrO₄^2–

Permanganate anion

MnO4−