Naming Compounds Ionic Compounds Binary Covalent Compounds

Naming Ionic Compounds Rule 1 The cation is written first in the name; the anion is written second in the name. Example: barium oxide BaO cation anion

Cations can be metals or polyatomic ions Examples: Na+ sodium ion (metal) NH4+ ammonium ion

Polyatomic Ions Polyatomic ions consist of more than one atom The atoms of a polyatomic ion are covalently bonded, so they stay together as a single, charged unit Example: NO3- nitrate ion

Rule 2 When the formula unit contains two or more of the same polyatomic ion, the polyatomic ion is written in parentheses with the subscript written outside the parentheses. Example: Ca(NO3)2

Rule 3 When the cation is a metal ion with a fixed charge, the name of the cation is the same as the element Example: Na+ = sodium When the cation is a metal ion with a variable charge, the charge on the cation is indicated using a Roman numeral, in parentheses, immediately following the name of the cation Example: Fe3+ = iron(III) Fe2+ = iron(II)

Anions can be negatively charged elements or polyatomic ions Examples: Cl- negatively charged element PO43- polyatomic anion

Rule 4 If the anion is a monatomic ion, the anion is named by adding the suffix -ide to the root of the element name Example: I- = iodide

Polyatomic ions which include oxygen in the anion use either the suffix -ate or -ite. The “ate” suffix contains more oxygen in the anion than one ending in “ite” Example: sulfate (SO42-) sulfite (SO32-)

Common Polyatomic Ions

Learning Check Name the following ionic compounds: Na2CO3 MgBr2 BaSO4 NH4OH

Naming Binary Covalent Compounds 1. The first element is named first, using the element’s name. 2. Second element is named as an Anion (suffix “-ide”) 3. Prefixes are used to denote the number of atoms 4. “Mono” is not used to name the first element

Prefixes for Naming Compounds number indicated mono- 1 di- 2 tri- 3 tetra- 4 penta- 5 hexa- 6 hepta- 7 octa- 8 nona- 9 deca- 10 Examples: CO carbon monoxide N2O dinitrogen oxide HI hydrogen iodide CCl4 carbon tetrachloride P2O5 diphosphorus pentoxide Prefixes are used for covalent compounds only

Learning Check Name the following compounds: PBr3 N2O4 SiCl4 CS2 H2Se