Nomenclature & Formulas

Cheat Sheet  ·  Chemistry Gr 11
Emil Oliversen
IONIC COMPOUNDS (NAMING)
Binary ionic: [metal] + [nonmetal stem]-ide
Fixed-charge
no Roman numeral needed
FIXED-CHARGE METALS
Na⁺
sodium
K⁺
potassium
Ca²⁺
calcium
Mg²⁺
magnesium
Al³⁺
aluminum
Ba²⁺
barium
VARIABLE-CHARGE METALS
Must use Roman numerals!
Fe²⁺/Fe³⁺
iron(II) / iron(III)
Cu⁺/Cu²⁺
copper(I) / copper(II)
Pb²⁺/Pb⁴⁺
lead(II) / lead(IV)
Sn²⁺/Sn⁴⁺
tin(II) / tin(IV)
Cr²⁺/Cr³⁺
chromium(II) / chromium(III)
Mn²⁺/Mn³⁺
manganese(II) / manganese(III)
EXAMPLES
NaCl
sodium chloride
FeCl₂
iron(II) chloride
FeCl₃
iron(III) chloride
MgO
magnesium oxide
Al₂O₃
aluminum oxide
POLYATOMIC IONS
Charge +1
NH₄⁺
ammonium
Charge −1
OH⁻
hydroxide
NO₃⁻
nitrate
NO₂⁻
nitrite
HCO₃⁻
hydrogen carbonate
ClO₄⁻
perchlorate
ClO₃⁻
chlorate
MnO₄⁻
permanganate
CH₃COO⁻
acetate
Charge −2
SO₄²⁻
sulfate
SO₃²⁻
sulfite
CO₃²⁻
carbonate
CrO₄²⁻
chromate
Cr₂O₇²⁻
dichromate
Charge −3
PO₄³⁻
phosphate
Pattern: -ate has more O than -ite. Same charge, one fewer oxygen atom.
POLYATOMIC EXAMPLES
Na₂SO₄
sodium sulfate
Ca(OH)₂
calcium hydroxide
NH₄Cl
ammonium chloride
Ca₃(PO₄)₂
calcium phosphate
MOLECULAR (COVALENT) COMPOUNDS
Nonmetal + nonmetal → Greek prefixes
#Prefix#Prefix
1mono5penta
2di6hexa
3tri7hepta
4tetra8octa
Mono omitted from 1st element if only one atom (except CO).
CO
carbon monoxide
CO₂
carbon dioxide
N₂O
dinitrogen monoxide
N₂O₄
dinitrogen tetroxide
PCl₅
phosphorus pentachloride
SO₃
sulfur trioxide
BINARY ACIDS
hydro[stem]ic acid (H + nonmetal, no O)
HCl (aq)
hydrochloric acid
HBr (aq)
hydrobromic acid
H₂S (aq)
hydrosulfuric acid
HF (aq)
hydrofluoric acid
OXYACIDS
-ate ion → -ic acid  |  -ite ion → -ous acid
H₂SO₄
sulfuric acid (sulfate)
H₂SO₃
sulfurous acid (sulfite)
HNO₃
nitric acid (nitrate)
HNO₂
nitrous acid (nitrite)
H₃PO₄
phosphoric acid (phosphate)
CRISS-CROSS METHOD
Swap magnitudes of charges as subscripts. Simplify.
Ca²⁺ + Cl⁻
Ca¹Cl₂ = CaCl₂
Al³⁺ + O²⁻
Al₂O₃
Mg²⁺+SO₄²⁻
Mg₂(SO₄)₂ → MgSO₄
Ca²⁺+NO₃⁻
Ca(NO₃)₂
Al³⁺+PO₄³⁻
Al₃(PO₄)₃ → AlPO₄
BRACKETS RULE
  • Polyatomic with subscript > 1 → use brackets
  • Ca(NO₃)₂ not CaNO₃₂
  • Subscript of 1 = never written
  • Always simplify subscripts (GCD)
VERIFY CHARGE = ZERO
CaCl₂
+2 + 2(−1) = 0 ✓
Al₂O₃
2(+3) + 3(−2) = 0 ✓
Ca₃(PO₄)₂
3(+2) + 2(−3) = 0 ✓
COMMON MISTAKES
  • Transition metals NEED Roman numerals
  • Simplify: Ca₂S₂ → CaS
  • "mono" on 2nd element always; 1st only if > 1
  • -ate ion → -ic acid (NOT -ous)
  • -ite ion → -ous acid (NOT -ic)
  • Greek prefixes: molecular only, NOT ionic
  • Binary acid: needs "hydro-" prefix
  • Polyatomic ions: memorize — do not guess
Check: sum of all charges in formula = 0