Names and Formulas for Ionic and Polyatomic Compounds

Vocabulary flashcards covering the concepts, rules, nomenclature, and common formulas of monatomic and polyatomic ionic compounds.

Formula unit

The simplest ratio of cations to anions in an ionic compound.

Monatomic ion

An ion formed from one atom, having a charge that is equal to its oxidation number.

Polyatomic ion

An ion made up of more than one atom that acts as an individual, single unit whose charge applies to the entire group of atoms.

Roman numerals (in ionic naming)

Numerals used in chemical nomenclature to indicate the oxidation number of cations having multiple possible oxidation states.

Parentheses in polyatomic formulas

Symbols placed around a polyatomic ion in a chemical formula with a subscript written outside to indicate that more than one unit of the ion is present.

Ammonium ion

A polyatomic cation with the formula $NH_4^+$ and a charge of $1+$.

Phosphate ion

A polyatomic anion with the formula $PO_4^{3-}$ and a charge of $3-$.

Calcium phosphate

An ionic compound often used in fertilizers, composed of three $Ca^{2+}$ ions and two $PO_4^{3-}$ ions to yield the chemical formula $Ca_3(PO_4)_2$.

Ammonium oxide

An ionic compound with the formula $(NH_4)_2O$, formed by combining two $NH_4^+$ ions with one $O^{2-}$ ion to balance charges.

Nitrate ion

A common polyatomic anion with the formula $NO_3^-$ and a $1-$ charge.

Nitrite ion

A common polyatomic anion with the formula $NO_2^-$ and a $1-$ charge.

Hydroxide ion

A polyatomic anion with the formula $OH^-$ and a $1-$ charge.

Cyanide ion

A polyatomic anion with the formula $CN^-$ and a $1-$ charge.

Permanganate ion

A polyatomic anion with the formula $MnO_4^-$ and a $1-$ charge.

Carbonate ion

A polyatomic anion with the formula $CO_3^{2-}$ and a $2-$ charge.

Sulfate ion

A polyatomic anion with the formula $SO_4^{2-}$ and a $2-$ charge.

Sulfite ion

A polyatomic anion with the formula $SO_3^{2-}$ and a $2-$ charge.

Acetate ion

A polyatomic anion with the formula $C_2H_3O_2^-$ and a $1-$ charge.

Dichromate ion

A polyatomic anion with the formula $Cr_2O_7^{2-}$ and a $2-$ charge.

Chromate ion

A polyatomic anion with the formula $CrO_4^{2-}$ and a $2-$ charge.