Polyatomic Ions

Oxyanion

A polyatomic ion containing a central atom bonded to one or more oxygen atoms, carrying a net negative charge.

-ate vs -ite

-ate is the base ion with more oxygens; -ite has one FEWER oxygen than -ate while keeping the same charge.

Hyper vs Hypo

per- means one MORE oxygen than the -ate ion; hypo- means one FEWER oxygen than the -ite ion, keeping charge constant.

Chlorine Oxyanion Family

Series of four ions with a constant -1 charge: Hypochlorite (ClO⁻), Chlorite (ClO₂⁻), Chlorate (ClO₃⁻), Perchlorate (ClO₄⁻).

Nitrogen Oxyanion Family

Two common nitrogen ions with a constant -1 charge: Nitrite (NO₂⁻) and Nitrate (NO₃⁻).

Sulfur Oxyanion Family

Two common sulfur ions with a constant -2 charge: Sulfite (SO₃²⁻) and Sulfate (SO₄²⁻).

Ammonium

The only common positively charged polyatomic ion with the formula NH₄⁺.

Hydroxide

A basic polyatomic anion with the formula OH⁻.

Nitrate

A highly soluble nitrogen-based oxyanion with the formula NO₃⁻.

Nitrite

A nitrogen-based oxyanion with the formula NO₂⁻.

Sulfate

A sulfur-based oxyanion with the formula SO₄²⁻.

Sulfite

A sulfur-based oxyanion with the formula SO₃²⁻.

Carbonate

A carbon-based oxyanion with the formula CO₃²⁻.

Bicarbonate (Hydrogen Carbonate)

An oxyanion formed by adding H⁺ to carbonate, resulting in the formula HCO₃⁻.

Phosphate

A phosphorus-based oxyanion with the formula PO₄³⁻.

Acetate

An organic polyatomic anion with the formula C₂H₃O₂⁻ (or CH₃COO⁻).

Chlorate

The standard chlorine-based oxyanion with the formula ClO₃⁻.

Chlorite

A chlorine-based oxyanion with the formula ClO₂⁻.

Perchlorate

The highest oxygen chlorine-based oxyanion with the formula ClO₄⁻.

Hypochlorite

The lowest oxygen chlorine-based oxyanion with the formula ClO⁻.

Permanganate

A dark purple transition metal oxyanion and powerful oxidizer with the formula MnO₄⁻.

Chromate

A chromium-based oxyanion with the formula CrO₄²⁻.

Dichromate

An orange oxyanion containing two chromium atoms with the formula Cr₂O₇²⁻.

Cyanide

A highly toxic diatomic carbon-nitrogen anion with the formula CN⁻.

Thiocyanate

An anion structurally similar to cyanide containing sulfur, with the formula SCN⁻.

Peroxide

A diatomic oxygen anion with a single covalent bond and a net formula of O₂²⁻.