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 2 Diatomic molecules- elements that exist as two atoms covalently bonded (H 2, N 2, O 2, F 2, Cl 2, Br 2, I 2 ) 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: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 Anion- accepts e- to achieve octet – F: 1s 2 2s 2 2p 5

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, MgCl 2, AlCl 3  Monatomic ion- a one-atom ion, EX: Mg 2+, Br –  Oxidation number- the charge of a monatomic ion  Polyatomic ion- ions made up of more than one atom EX: NH 4 +, SO 4 2-

Ionic Formulas  Ex: sodium oxide  Identify charge on metal and nonmetal ions- (Ex: Na +, O 2- )  Criss-cross superscripts to balance charges (Ex: Na 2 O)  Check if total formula has 0 charge  Write answer with subscripts (Ex: Na 2 O)  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: CaSO 4 = calcium sulfate)  If last ion is monatomic, add –ide at end  (Ex: CaCl 2 = calcium chloride)

Practice Naming Ionic Compounds  CaO  Na 2 SO 4  Ca 3 (PO 4 ) 2  MgSO 3

Transition Metals- The Stock System  Some metals can exist in several forms  Ex: Cu 1+, Cu 2+  Chemical formula used to decide which ion is present  (Ex: CuCl 2 – must be Cu 2+  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  PbO 2  Fe 2 (SO 4 ) 3

8.4 Metallic Bonds  Electron Sea Model for delocalized electrons  All atoms contribute their electrons to the community