Memorization of Polyatomics and Solubility

OH⁻

Hydroxide

CN⁻

Cyanide

SCN⁻

Thiocyanate

ClO⁻

Hypochlorite

ClO₂⁻

Chlorite

ClO₃⁻

Chlorate

ClO₄⁻

Perchlorate

CH₃COO⁻ (C₂H₃O₂⁻)

Acetate

C₂O₄²⁻

Oxalate

S₂O₃²⁻

Thiosulfate

CrO₄²⁻

Chromate

Cr₂O₇²⁻

Dichromate

NO₂⁻

Nitrite

NO₃⁻

Nitrate

SO₃²⁻

Sulfite

SO₄²⁻

Sulfate

O₂²⁻

Peroxide

CO₃²⁻

Carbonate

HCO₃⁻

Hydrogen carbonate (bicarbonate)

PO₃³⁻

Phosphite

PO₄³⁻

Phosphate

NH₄⁺

Ammonium

H₃O⁺

Hydronium

-ate vs -ite: which has more oxygens?

-ate has one more O than -ite (NO₃⁻ vs NO₂⁻)

Chlorine oxyanion order (fewest to most O)

ClO⁻ hypochlorite; ClO₂⁻ chlorite; ClO₃⁻ chlorate; ClO₄⁻ perchlorate

Charge of -ate and -ite pairs in the same family

Same charge (only the O count changes)

Rule 1: Group 1 (Li⁺ Na⁺ K⁺ Rb⁺ Cs⁺) and NH₄⁺ salts

SOLUBLE

Rule 2: NO₃⁻ CH₃COO⁻ ClO₄⁻ salts

SOLUBLE

Rule 3: Ag⁺ Pb²⁺ Hg⁺ (Hg₂²⁺) salts

Mostly INSOLUBLE

Rule 4: Cl⁻ Br⁻ I⁻ salts

SOLUBLE (except with Ag⁺ Pb²⁺ Hg⁺ from Rule 3)

Rule 5: CO₃²⁻ PO₄³⁻ S²⁻ OH⁻ O²⁻ CrO₄²⁻ salts

INSOLUBLE (but sulfides and hydroxides of Ca²⁺ Sr²⁺ Ba²⁺ are slightly soluble)

Rule 6: SO₄²⁻ salts

SOLUBLE except Ca²⁺ Sr²⁺ Ba²⁺ (those are INSOLUBLE)

Hydroxide

OH⁻

Cyanide

CN⁻

Thiocyanate

SCN⁻

Hypochlorite

ClO⁻

Chlorite

ClO₂⁻

Chlorate

ClO₃⁻

Perchlorate

ClO₄⁻

Acetate

CH₃COO⁻ (C₂H₃O₂⁻)

Oxalate

C₂O₄²⁻

Thiosulfate

S₂O₃²⁻

Chromate

CrO₄²⁻

Dichromate

Cr₂O₇²⁻

Nitrite

NO₂⁻

Nitrate

NO₃⁻

Sulfite

SO₃²⁻

Sulfate

SO₄²⁻

Peroxide

O₂²⁻

Carbonate

CO₃²⁻

Hydrogen carbonate (bicarbonate)

HCO₃⁻

Phosphite

PO₃³⁻

Phosphate

PO₄³⁻

Ammonium

NH₄⁺

Hydronium

H₃O⁺

Group 1 cations (Li⁺ Na⁺ K⁺ Rb⁺ Cs⁺) and NH₄⁺ salts

Rule 1: SOLUBLE

NO₃⁻ CH₃COO⁻ ClO₄⁻ salts

Rule 2: SOLUBLE

Ag⁺ Pb²⁺ Hg⁺ (Hg₂²⁺) salts

Rule 3: Mostly INSOLUBLE

Cl⁻ Br⁻ I⁻ salts

Rule 4: SOLUBLE (except with Ag⁺ Pb²⁺ Hg⁺)

CO₃²⁻ PO₄³⁻ S²⁻ OH⁻ O²⁻ CrO₄²⁻ salts

Rule 5: INSOLUBLE (sulfides and hydroxides of Ca²⁺ Sr²⁺ Ba²⁺ are slightly soluble)

SO₄²⁻ salts

Rule 6: SOLUBLE except Ca²⁺ Sr²⁺ Ba²⁺ (INSOLUBLE)

Rule 1

Group 1 (Li⁺ Na⁺ K⁺ Rb⁺ Cs⁺) and NH₄⁺ salts are SOLUBLE

Rule 2

NO₃⁻ CH₃COO⁻ ClO₄⁻ salts are SOLUBLE

Rule 3

Ag⁺ Pb²⁺ Hg⁺ salts are mostly INSOLUBLE

Rule 4

Cl⁻ Br⁻ I⁻ salts are SOLUBLE (except Ag⁺ Pb²⁺ Hg⁺)

Rule 5

CO₃²⁻ PO₄³⁻ S²⁻ OH⁻ O²⁻ CrO₄²⁻ salts are INSOLUBLE (Ca²⁺ Sr²⁺ Ba²⁺ sulfides and hydroxides slightly soluble)

Rule 6

SO₄²⁻ salts are SOLUBLE except Ca²⁺ Sr²⁺ Ba²⁺