Ionic bonds and Compounds

TYPES OF BONDS

IONIC BONDS COVALENT BONDS

• transfer of electrons• between a Cation and an Anion• resulting bond is neutral

• sharing of electrons• between two or more nonmetals• Two types- polar or non-polar

Example NaCl MgSO4

Example H2O Cl2

ionic compounds consist of a combination of cations and an anions

• the formula is always the same as the empirical formula

• the sum of the charges on the cation(s) and anion(s) in each formula unit must equal zero

The ionic compound NaCl

Most ionic compounds form Crystalline StructureMost ionic compounds form Crystalline Structure

• Formulas for ionic compounds are generally empirical formulas.• Ionic compounds are electronically neutral.

Naming Ions and Ionic CompoundsNaming Ions and Ionic Compounds

To name ionic compounds:

1) Name the cation omit the word ionuse a Roman numeral if the cation can have more than one chargeIf the element has latin name use classical method

2) Name the anionomit the word ionExamples:NaCN sodium cyanideFeCl2 iron(II) chloride Ferrous ChlorideFeCl3 iron(III) chloride Ferric Chloride

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 CompoundsFormulas of Ionic Compounds

Formulas of Ionic CompoundsFormulas of Ionic Compounds

Calcium phosphate:

5.7

Ca2+ PO43–

Ca3(PO4)2

Sum of charges: 3(+2) + 2(–3) = 0

Ionic compounds with polyatomic ions

HydratesHydrates

A hydrate is an ionic compound that has a specific number of water molecules within its solid structure.For example, in its normal state, copper(II) sulfate has five water molecules associated with it.

Systematic name: copper(II) sulfate pentahydrateFormula: Cu(SO)4 ∙ 5H2O

Some other hydrates areBaCl2 ∙ 2H2O Can you name them???LiCl ∙ H2OMgSO4 ∙ 7H2OSr(NO3)2 ∙ 4H2O

HydratesHydrates

When the water molecules are driven off by heating, the resulting compound, Cu(SO)4, is sometimes called anhydrous copper(II) sulfate.

Anhydrous means the compound no longer has water molecules associated with it.

Worked Example 5.9

Strategy Begin by identifying the cation and anion in each compound, and then combine the names for each, eliminating the word ion.

Name the following ionic compounds: (a) Fe2(SO4)3, (b) Al(OH)3, and (c) Hg2O.

Solution (a) Fe2(SO4)3 is iron(III) sulfate.

(b) Al(OH)3 is aluminum hydroxide.

(c) Hg2O is mercury(I) oxide.

Think About It Be careful not to confuse the subscript in the formula with the charge in the metal ion. In part (a), for example, the subscript on Fe is 2, but this is an iron(III) compound.

Formula of Ionic Compounds

Al2O3

2 x +3 = +6 3 x -2 = -6

Al3+ O2-

CaBr2

1 x +2 = +2 2 x -1 = -2

Ca2+ Br-

Na2CO3

1 x +2 = +2 1 x -2 = -2

Na+ CO32-

Recognizing Ionic Compounds

A compound is ionic if it contains a metal from group 1Or group 2 or one of the polyatomic ions. Binary metal Oxides and sulfides also have ionic character

Fig 2-23Pg 59

Pure water(left) and a solution of sugar(right) do not conduct electricitybecause they contain virtually no ions. Asolution of salt (center) conducts electricity wellbecause it contain mobile cations and anions.Courtesy Ken Karp

Chemical Nomenclature• Ionic Compounds

– often a metal + nonmetal– anion (nonmetal), add “ide” to element name

BaCl2 barium chloride

K2O potassium oxide

Mg(OH)2 magnesium hydroxide

KNO3 potassium nitrate

Cations of Variable Charge

Transition metals such as copper may form cationsOf different charge. This is represented by placing aRoman numeral after the transition metal in Parentheses after the name of the metal.

CuO Copper(II) oxideCu2O Copper(I) oxide

• Transition metal ionic compounds– indicate charge on metal with Roman numerals

FeCl2 2 Cl- -2 so Fe is +2 iron(II) chloride

FeCl3 3 Cl- -3 so Fe is +3 iron(III) chloride

Cr2S3 3 S-2 -6 so Cr is +3 (6/2) chromium(III) sulfide

Hydrates

A hydrate is an ionic compound that has water moleculesIncorporated into their solid structures

Writing the formula: name of ionic compound-# H2O

Pg 89

The Hydrate of coppersulfate is the pentahydrate,and the anhydrous coppersulfate will absorb water to form the Hydrate.

CuSO4 5 H2O.

Copper(II)sulfate.pentahydrate

Olmsted Williams