Ionic and Covalent bonding Chapters 15 and 16

Lewis Dot Diagrams Ex) Draw the Lewis Dot diagram for oxygen (atomic #8) step # 1) determine the number of valence electrons (electrons in outer level) Oxygen is in group 6 A oxygen has 6 valence electrons Step # 2) Draw dot structure . . . O : .

Si . . . . Ex) Draw a Lewis Dot diagram for silicon (atomic #14). step #1 determine valence electrons Silicon is in group 4A silicon has 4 valence electrons step # 2) Draw dot structure . . . Si .

Octet Rule: atoms having 8 electrons in their outer level have the highest degree of stability. - electrons can be transferred (ionic bond) or shared (covalent bond) for the atom to achieve a total of eight electrons - the Noble Gases already have eight electrons which is why they are unreactive.

Br K K+ + Br - KBr . . . . : . . Ex) potassium & bromine Ionic Bond - electrostatic force that holds two atoms together due to a difference in charge -electrons are transferred usually from a metal to a nonmetal Ex) potassium & bromine e- transferred . . . o Br K . : . . K+ + Br - KBr

Ex) Use Lewis dot diagrams to determine the formula of calcium fluoride. . . o F . : . . . Ca . 2e- transferred . . F o . : . . Ca+2 + 2 F - CaF2

Properties of Ionic Compounds - are solid, generally forming crystals - have high melting points (because their bonds are so strong) - conduct electricity in the molten state and when dissolved in water Metallic Bond - chemical bond that occurs between pure metals - electrons are free to drift from atom to atom - positive charge on nucleus pulls any electron toward it, even if it is from a different atom

Covalent Bond - attractive force between two atoms that share electrons to form molecular cmpds. Ex) H2O H H x . . x . H . O : O : x . . . . H x

Types of Covalent Bonds I) Single bond: one pair of electrons are shared Ex) Cl2 . . . . . . . . . . Cl Cl Cl x Cl : : : : x . . . . . . . . Cl Cl structural formula:

. . C C . . C C H H H H H H H H II) Double bond : two pairs of electrons are shared (4 electrons total) . H H . x Ex) C2H4 (ethene) x C C x x . . x x x x H H H H C C structural formula H H

. . C C C C H H H H III) Triple bond : three pairs of electrons are shared (6 electrons total) . . Ex) C2H2 (ethyne) C C H x x x H x x x x x C C H H structural formula

Examples of covalent bonds . . H H H H 1) H2 . . . . . . 2) O2 . . O O O O . . . . . . . . O . O . 3) H2O . . H H H H

. . . . 4) NH3 . . . . H N H H N H . . H H . . . . . . . . . . C . . . O O . 5) CO2 . . O C O

coordinatecovalent bond IV) Coordinate Covalent bond: one atom contributes all of the electrons to that bond. coordinatecovalent bond . . Ex) SO2 . S . . . . x . . . x O . . O . . . .

O O O O O O or V) Resonant bond: bond will resonate between different locations . . Ex) O3 . . . . . O O O . . . . . or . . . . . . . O O O . . . . .

DEN = 0.0 - 0.4 DEN = 0.4 - 2.0 DEN > 2.0 covalent ionic polar covalent ionic

H H O O H H . . : . . d+ d+ d- VII) Polar bond: (polar covalent) - unequal sharing of electrons - one atom holds electrons more tightly due to greater electronegativity - creates a partial positive & partial negative charge on the molecule H d+ H . x O . O : x H H . . d+ d-

O H H H O H O H H .... Hydrogen bond: -partial charge on a hydrogen atom bonds to partial charge on another atom - has about 5% of the strength of a covalent bond d- O d+ d+ d+ H H H .... O H O d- H d- d+ d+ H d+