1. Chapter 8 Ionic Bonding

2. Ionic Compounds/ Chemical Bnds  Chem Bond: force that holds 2 atoms together.  Arises from attraction of positive nucleus and neg. e’s  Or from attraction of positive ions and neg.ions  Review valence e’s and dot structures

3. Formation of + ions (cations)  When atom loses one or more valence e’s to have octet.  Atom will become ion and become +.  1e lost→+1 ion, 2e’s lost →+2 ion, 3e’s lost →+ 3 ion  Then ion will have e config. of noble gas. – Na+ has config. of [Ne] from [Ne]3s 1 – Mg +2 has config. of [Ne] from [Ne]3s 2

4. Formation of Negative Ions (Anions)  On right side of P.T. nonmetals will not lose e’s, but gain e’s.  F atom has config. of [He]2s 2 2p 5, gains 1e to be [He] 2s 2 2p 6 or [Ne].  S atom has config. of [Ne]3s 2 3p 4, gains 2e to be [Ne]3s 2 3p 6 or [Ar].  These ions(+ or -) do not become those noble gases; their e’s are just in same places and have same stability.

5. Result?  Then + ions (cations) attract – ions (anions). Not just one attracting one other, but large numbers of each come together to form a crystal-lattice. See p217  Greater the attractions between +and – ions, the higher the m.pt., b.pt., and hardness. (Requires more energy to break strong bonds.)

6. Names & formulas for Ionic Cpds.  Simplest ratio of ions (formula) is called a formula unit.  NaCl, MgBr 2, KI are technically formula units, not molecules.

7. Oxidation Number of Ions  Sometimes called charge or oxidation state.  Both interchangeable.  Many transition metals have multiple ox. Numbers.  Gr I is +1, Gr II is +2.

8. To write correct formula  Write ions with charges, put + 1 st, then –ion.  Check to see if charges add up to zero. –If so, write as is. –If not, cross charge numbers (not sign). –Multiply up and check for adding up to zero. –CHARGE OF COMPOUND must be ZERO.

9.  Examples: sodium sulfide, aluminum chloride, magnesium oxide, calcium iodide. P. 224-226.  If polyatomic ion, same idea.  Transparency, 8-5

10. Metallic Bonds and Properties of Metals  Metals are not ionic, but have some similar characteristics.  Why? Because ionic cpds. Have + and – particles and metals have + and – regions as well.  Metals’ structure sometimes is referred to as a “sea of electrons” or delocalized e’s.

11.  This means there are + nuclei lined up and e’s from those metal atoms flow in and out around those nuclei.  See p. 228 or draw on board.  This “sea” causes a number of specific metallic properties. –High m.pt., and b.pt. –Malleable, ductile, lustrous

12. Metal alloys  A mixture of elements with metallic properties.  Steel is Fe and other elements.  2 types alloys –Substitutional: some atoms are replaced by other metal atoms. (brass- copper & zinc) –Interstitial: has small holes filled by other small atoms. (carbon steel)