Polyatomic Ions

Acetate

C₂H₃O₂⁻

Carbonate

CO₃²⁻

Hydrogen carbonate (bicarbonate)

HCO₃⁻

Hydroxide

OH⁻

Nitrite

NO₂⁻

Nitrate

NO₃⁻

Chromate

CrO₄²⁻

Dichromate

Cr₂O₇²⁻

Phosphate

PO₄³⁻

Hydrogen phosphate

HPO₄²⁻

Dihydrogen phosphate

H₂PO₄⁻

Ammonium

NH₄⁺

Hypochlorite

ClO⁻

Chlorite

ClO₂⁻

Chlorate

ClO₃⁻

Perchlorate

ClO₄⁻

Permanganate

MnO₄⁻

Sulfite

SO₃²⁻

Hydrogen sulfite (bisulfite)

HSO₃⁻

Sulfate

SO₄²⁻

Hydrogen sulfate (bisulfate)

HSO₄⁻

Cyanide

CN⁻

Peroxide

O₂²⁻

Alkali Metal + Water Reaction

2M + 2H₂O → 2MOH(aq) + H₂(g); alkali metals react with water to form dissolved metal ions, hydroxide ions, and hydrogen gas.

Metal Halides

M + X₂ → MX (general skeleton); halogens react with metals to form metal halides.

Hydrogen Halides

H₂ + X₂ → 2HX (general skeleton); halogens react with hydrogen to form hydrogen halides.

Interhalogen Compounds

X₂ + Y₂ → 2XY (general skeleton); different halogens react with each other to form interhalogen compounds.

Soluble Compounds: Group 1, Ammonium, Nitrate, and Acetate

Li⁺, Na⁺, K⁺, NH₄⁺, NO₃⁻, and C₂H₃O₂⁻ compounds are soluble.

Soluble Compounds: Halides

Cl⁻, Br⁻, and I⁻ compounds are soluble except when paired with Ag⁺, Hg₂²⁺, or Pb²⁺.

Soluble Compounds: Sulfates

SO₄²⁻ compounds are soluble except when paired with Sr²⁺, Ba²⁺, Pb²⁺, Ag⁺, or Ca²⁺.

Insoluble Compounds: Hydroxides and Sulfides

OH⁻ and S²⁻ compounds are insoluble except when paired with Li⁺, Na⁺, K⁺, or NH₄⁺.

Soluble Sulfides

S²⁻ compounds paired with Ca²⁺, Sr²⁺, or Ba²⁺ are soluble.

Slightly Soluble Hydroxides

OH⁻ compounds paired with Ca²⁺, Sr²⁺, or Ba²⁺ are slightly soluble.

Insoluble Compounds: Carbonates and Phosphates

CO₃²⁻ and PO₄³⁻ compounds are insoluble except when paired with Li⁺, Na⁺, K⁺, or NH₄⁺.