NAMING IONIC AND COVALENT COMPOUNDS#nameshavemeaning

A compound is a substance composed of two or more elements combined in a specific ratio and held together by chemical bonds.

Familiar examples of compounds are water and salt (sodium chloride).

Compounds

IONIC COMPOUNDS AND BONDING

The resulting electrically neutral compound, sodium chloride, is represented with the chemical formula NaCl.

The chemical formula, or simply formula, of an ionic compound denotes the constituent elements and the ratio in which they combine.

A monatomic ion is named by changing the ending of the element’s name to –ide.

Cl– is chloride O2– is oxide

Some metals can form cations of more than one possible charge.

Fe2+ : ferrous ion [Fe(II)]Fe3+ : ferric ion [Fe(III)]

Mn2+ : manganese(II) ionMn3+ : manganese(III) ionMn4+ : manganese(IV) ion

NAMING IONS AND IONIC COMPOUNDS

Naming Ions and Ionic Compounds

NAMING IONS AND IONIC COMPOUNDS

Formulas for ionic compounds are generally empirical formulas.

Ionic compounds are electronically neutral.

Al3+ O2–

Al2O3

In order for ionic compounds to be electronically neutral, the sum of the charges on the cation and anion in each formula must be zero.

Aluminum oxide:

Sum of charges: 2(+3) + 3(–2) = 0

Formulas of Ionic Compounds

Formulas of Ionic Compounds

NAMING IONS AND IONIC COMPOUNDS

To name ionic compounds:

1) Name the cation omit the word ion use a Roman numeral if the cation can have more than one

charge

2) Name the anion omit the word ion

Examples:NaCN sodium cyanideFeCl2 iron(II) chlorideFeCl3 iron(III) chloride

Polyatomic ions consist of a combination of two or more atoms.

Formulas are determined following the same rule as for ionic compounds containing only monatomic ions: ions must combine in a ratio that give a neutral formula overall.

Calcium phosphate:

COVALENT BONDING IN IONIC SPECIES

Ca2+ PO43–

Ca3(PO4)2

Sum of charges: 3(+2) + 2(–3) = 0

Remember that binary molecular compounds are substances that consist of just two different elements.

Nomenclature:1) Name the first element that appears in the formula.

2) Name the second element that appears in the formula, changing its ending to –ide.

Examples:HCl hydrogen chloride

HI hydrogen iodide

NAMING MOLECULAR COMPOUNDS

Greek prefixes are used to denote the number of atoms of each element present.

Naming Molecular Compounds

The prefix mono- is generally omitted for the first element.

For ease of pronunciation, we usually eliminate the last letter of a prefix that ends in “o” or “a” when naming an oxide.

Example: N2O5 is dinitrogen pentoxide not dinitrogen pentaoxide

Naming Molecular Compounds

WORKED EXAMPLE 5.7

Strategy Each compound will be named using the systematic nomenclature including, where necessary, appropriate Greek prefixes.

Name the following binary molecular compounds: (a) NF3 and (b) N2O4.

Solution (a) nitrogen trifluoride

(b) dinitrogen tetroxide

Think About It Make sure that the prefixes match the subscripts in the molecular formulas and that the word oxide is not preceded immediately by an “a” or an “o”.

WORKED EXAMPLE 5.8

Strategy The formula for each compound will be deduced using the systematic nomenclature guidelines.

Write the chemical formulas for the following binary molecular compounds: (a) sulfur tetrafluoride and (b) tetraphosphorus decasulfide.

Solution (a) SF4(b) P4S10

Think About It Double-check that the subscripts in the formulas match the prefixes in the compound names: (a) 4 = tetra and (b) 4 = tetra and 10 = deca.

FOLLOW UP

• What is the name of KF?• Potasium Floride

• What is the name of H2O?• Dihydrogen Monoxide

• What is the name of CaCl2?• Calcium Chloride