Ch. 6 Bonding 6.3 Ionic Bonding

Ionic Compounds ionic bonds do NOT form molecules chemical formulas for ionic compounds represent the simplest ratio of ion types made of anions and cations

Ionic Compounds combined so that amount of positive and negative charge is equal usually crystalline solid formula of ionic compound depends on the charges of the ions combined

Formation attractive forces: repulsive forces: oppositely charged ions nuclei and electron clouds of adjacent ions repulsive forces: like-charged ions 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

Formation specific lattice pattern created depends on: charges of ions size of ions Calcium Bromide: each Ca2+ is surrounded by 8 F- each F- is surrounded by 4 Ca2+ Sodium Chloride each Na+ is surrounded by 6 Cl- each Cl- is surrounded by 6 Na+

Lattice Energy energy released when separate gaseous ion bond to form ionic solid the larger the amount of energy released, the stronger the bond since it is released, the value is negative NaCl -787.5 NaBr -751.4 CaF2 -2634.7 CaO -3385 LiCl -861.3 MgO -3760 KCl -715

Ionic vs. Molecular ionic bonds and molecular bonds are both strong ionic bonds connect all ions together molecules are more easily pulled apart because intermolecular forces are weak

Ionic vs. Molecular Molecular Compounds: low melting and boiling points many are gases at room temperature Because the intermolecular forces of the molecules are weak so they are easily separated

Ionic vs. Molecular Ionic Compounds: higher melting and boiling points all are solid at room temperature hard: Because of the strong forces, it is difficult for one layer of ions to move past another brittle: if one layer is moved, the layers come apart completely

Ionic vs. Molecular Ionic Compounds: good conductors in liquid state Because ions are free to move and carry charge poor conductor in solid state Because ions are fixed in place

Polyatomic Ions charged group of covalently bonded atoms Example: CN-

NH4+ : ammonium ion

O O S O O O H SO42- : sulfate ion OH- : hydroxide ion 5 x 6 = 30 total = 30 + 2 = 32 OH- : hydroxide ion 6 + 1 + 1 = 8 total O S O O O H