CHAPTER 9
Covalent Bonding
What You Will Learn…The nature of the covalent bondHow to name covalently bonded groups of atomsShapes of moleculesCharacteristics of covalent moleculesHow to compare and contrast polar and nonpolar molecules
Why It Is Important
Most compounds are covalently bonded
Including those in living organisms
AssignmentWrite out Chapter 9 vocabulary words and their definitions
14 words on page 271PLUS the octet rule from Chapter 6
The Covalent Bond
Section 9.1
ObjectivesApply the octet rule to atoms that bond covalentlyDescribe the formation of single, double, and triple covalent bondsCompare and contrast sigma and pi bondsRelate the strengths of covalent bonds to bond length and bond dissociation energy
Key TermsCovalent bondMoleculeLewis structure
Sigma bondPi bondEndothermicExothermic
Review Do noble gases bond?
Why or why not?What is an ionic bond?Fill in the blank:
In an ionic bond, electrons are_________from one ion to another.
What if both atoms need
valence electrons?
Sharing ElectronsAnother way atoms acquire noble gas configurationsOccurs when BOTH atoms want to gain valence electrons
What is the Octet Rule from Chapter
6?
Covalent BondBond that results from sharing valence electrons
Shared electrons become part of BOTH atoms’ outer energy level
Most between NONMETALS
Covalent vs Ionic
MoleculeFormed when two or more atoms bond covalently
Covalent bonds are often called molecular bonds
Diatomic MoleculesTwo atoms of the same element form a bondAttractive forces = Repulsive forcesExamples:
H2
O2
N2
Halogens: F2, Cl2, Br2, I2
Diatomic Fluorine
Each Fluorine has 3 lone pairs and 1 shared pair of electrons
Single Covalent Bond
2 electrons (or 1 pair) are shared between two atoms
Single Covalent Bond
Lewis StructureElectron-dot diagrams for moleculesDots represent lone pairs of electronsA line represents shared electrons
Lewis Structures
H-H
H ö:
H
Lewis StructuresGroup 7A Elements
7 valence electrons, need 1 more, form one single bond
Lewis StructuresGroup 6A Elements
6 valence electrons, need 2 more, form 2 single bonds
Lewis StructuresGroup 5A Elements
5 valence electrons, need 3 more, form 3 single bonds
Lewis StructuresGroup 4A Elements
4 valence electrons, need 4 more, form 4 single bonds
Practice Problems
Practice ProblemSection 9.1 #1 on page 874
Sigma BondAnother name for single covalent bonds
Electron pair is shared in the area centered between atomsValence orbitals overlap end to ends and s; s and p; p and p
Multiple Covalent Bonds
Atoms form noble gas configuration by sharing more than one pair or electrons between 2 atomsC, N, O, S
Double Bond2 pairs (or 4 electrons) of electrons are shared
Triple Bond3 pairs (or 6 electrons) of electrons are shared
Pi BondFormed when parallel orbits overlap to share electronsShared par occupies the space above and below the line that represents where the 2 atoms join together
Multiple Bonds1 sigma bondAt least 1 pi bond
Double Bond1 sigma bond1 pi bond
Triple BondOne sigma bondTwo pi bonds
Pi and Sigma
Strength of Covalent Bond
Distance between nucleiBond length= distance at maximum attraction
Bond dissociation energy= energy required to break bonds
Exothermic Reaction
More energy is released forming new bonds than is required to break bonds in the initial reactants
Endothermic Reaction
Greater amount of energy is required to break the existing bonds in the reactants than is released when the new bonds form in the products
QUESTIONS?
Homework6-12 on page 247Bonding Problems