Ch. 6 Bonding

6.3 Ionic Bonding

Ionic Compounds

ionic bonds do NOT form moleculeschemical formulas for ionic compounds

represent the simplest ratio of ion types made of anions and cations

Ionic Compoundscombined so that positive charges balance

negative chargescrystalline solidformula of ionic compound depends of the

charges of the ions combined

Binary Ionic Compounds

Because positive charges must balance negative charges, use criss-cross method to make formulas. Write the formula for aluminum oxide.

Binary Ionic Compounds

If you don’t like criss-cross, use algebra. Write the formula for barium sulfide.

Formation

• attractive forces:– oppositely charged ions (main attraction)– nuclei and electron clouds of adjacent ions

• repulsive forces:– like-charged ions (main repulsion)– electrons of adjacent ions

Formation

distance between the ions creates a balance between those forces

ions minimize their PE by combining in an orderly arrangement called a crystal lattice

FormationSpecific lattice pattern created

depends on:charges of ions

– determines number of electrons transferred

– determines the ratio of ionssize of ions

– larger ions need more space

Lattice Energy

• energy released when separate gaseous ions bond to form ionic solid or the energy absorbed to break the bonds between ions

• the larger the amount of energy, the stronger the bond

• more electrons transferred or smaller ions leads to a larger lattice energy

NaCl -787.5

NaBr -751.4

CaF2 -2634.7

CaO -3385

LiCl -861.3

MgO -3760

KCl -715

In each of the following pairs of compounds, identify the one with the

higher lattice energy

KCl, CaS

LiF, NaCl

Fe2O3, MnO2

CaO, CaCl2