Chemical Naming & Formulas Cheat Sheet

Key Facts

• Ionic compounds are electrically neutral, so the total positive charge plus the total negative charge must equal $0$.
• Write the cation first and the anion second in an ionic formula, such as $\mathrm{Na}^{+}+\mathrm{Cl}^{-}\rightarrow \mathrm{NaCl}$.
• Use subscripts to balance ion charges, so $\mathrm{Mg}^{2+}+2\mathrm{Cl}^{-}\rightarrow \mathrm{MgCl}_{2}$.
• Use parentheses when more than one polyatomic ion is needed, as in $\mathrm{Al}^{3+}+\mathrm{SO}_{4}^{2-}\rightarrow \mathrm{Al}_{2}(\mathrm{SO}_{4})_{3}$.
• A Roman numeral in a metal name gives the metal ion charge, so iron(III) chloride contains $\mathrm{Fe}^{3+}$ and has the formula $\mathrm{FeCl}_{3}$.
• Binary covalent compounds use prefixes such as mono-, di-, tri-, tetra-, and penta-, so $\mathrm{CO}_{2}$ is carbon dioxide.
• For binary acids, use hydro- plus the nonmetal root plus -ic acid, so $\mathrm{HCl(aq)}$ is hydrochloric acid.
• For oxyacids, anions ending in -ate form -ic acids and anions ending in -ite form -ous acids, so $\mathrm{HNO}_{3}$ is nitric acid and $\mathrm{HNO}_{2}$ is nitrous acid.

Vocabulary

Cation

A cation is a positively charged ion that has lost one or more electrons.

Anion

An anion is a negatively charged ion that has gained one or more electrons.

Ionic compound

An ionic compound is a neutral compound made from cations and anions held together by electrostatic attraction.

Covalent compound

A covalent compound is a compound made of nonmetals that share electrons in chemical bonds.

Polyatomic ion

A polyatomic ion is a charged group of covalently bonded atoms that acts as one ion.

Oxidation number

An oxidation number is the charge an atom has or appears to have in a compound or ion.