CHAPTER 8

Ionic Compounds

Atoms vs Compounds

• Atom-smallest piece of matter that retains a material’s properties

• Molecule- atoms covalently bonded, bonded by the sharing of electrons

• Diatomic molecules- elements that exist as two atoms covalently bonded (H2, N22, O2, F2, Cl2, Br2, I2)

• Ionic compounds- ions bonded by their oppositely charged forces

8.1/ 8.2 Forming Ionic bonds• Ionic bonds- formed by the donation of

an electron from a (+) ion to a (-) ion EX: K+1 + F – 1 → KF (neutral)

• Cations and anions arrange into a crystal lattice:

• Cation- donates e- to achieve octet– K: 1s22s22p63s23p64s1

• Anion- accepts e- to achieve octet– F: 1s22s22p5

Ionic Crystal Lattice

Properties of Ionic Compounds

Solid Crystalline Brittle High melting point High boiling point Conducts electricity when dissolved in

water

8.2 Vocubulary

Electrolyte- an ionic compound whose aqueous solution conducts electric current

Lattice energy- energy required to separate one mole of the ions of an ionic compound

8.3 Formulas for Ionic Compounds Formula unit- simplest ratio of the ions

represented in an ionic compound EX: NaCl, MgCl2, AlCl3

Monatomic ion- a one-atom ion, EX: Mg2+, Br –

Oxidation number- the charge of a monatomic ion

Polyatomic ion- ions made up of more than one atom EX: NH4

+, SO42-

Ionic Formulas

Ex: sodium oxide Identify charge on metal and nonmetal

ions- (Ex: Na+, O2-) Criss-cross superscripts to balance

charges (Ex: Na2O) Check if total formula has 0 charge Write answer with subscripts (Ex: Na2O) Note: Polyatomic (many atom) ions are

same except parenthesis put around them before subscripts are added

Practice Writing Formulas

Lithium chloride Potassium sulfide Magnesium bromide Calcium oxide Sodium nitrate Sodium sulfate Calcium chlorate

Naming Ionic Compounds

NO PREFIXES If last ion is polyatomic, name normally (Ex: CaSO4 = calcium sulfate)

If last ion is monatomic, add –ide at end (Ex: CaCl2 = calcium chloride)

Practice Naming Ionic Compounds CaO

Na2SO4

Ca3(PO4)2

MgSO3

Transition Metals- The Stock System

Some metals can exist in several forms Ex: Cu1+, Cu2+

Chemical formula used to decide which ion is present (Ex: CuCl2 – must be Cu2+

Name puts metal ion charge in parenthesis Ex: copper (II) chloride

***only done for some transition metals

Practice the Stock System

Tin (II) oxide Iron (III) sulfide Copper (I) sulfate PbO PbO2

Fe2(SO4)3

8.4 Metallic Bonds

Electron Sea Model for delocalized electrons All atoms contribute their electrons to the

community