Covalent Bonds and Covalent Bonds and CompoundsCompounds

MoleculesMolecules

Three Kinds of BondsThree Kinds of Bonds

1.1. Non-metal to non-metalNon-metal to non-metal

2.2. metal to non-metalmetal to non-metal

3.3. metal to metalmetal to metal

CovalentCovalent IonicIonic MetallicMetallic

Why do atoms bond?Why do atoms bond?

To achieve stabilityTo achieve stabilityStability is achieved when octet rule is Stability is achieved when octet rule is

satisfiedsatisfied

Bonds and ElectronegativityBonds and Electronegativity

Electrons are Electrons are transferredtransferred between atoms between atoms when the difference in electronegativity when the difference in electronegativity between the atoms is quite high.between the atoms is quite high.

The amount of transfer depends on the The amount of transfer depends on the electronegativity difference.electronegativity difference.

Bonds and ElectronegativityBonds and Electronegativity

The number 1.67 seems to be the magic The number 1.67 seems to be the magic number.(Note:1.67 rounds to 1.7)number.(Note:1.67 rounds to 1.7)

If the electronegativity difference is less If the electronegativity difference is less than 1.67, the bond is more covalent than than 1.67, the bond is more covalent than ionic.ionic.

If the electronegativity difference is greater If the electronegativity difference is greater than 1.67, the bond is more ionic than than 1.67, the bond is more ionic than covalent.covalent.

Pg. 263 Figure 9-15Pg. 263 Figure 9-15

Electronegativity DifferenceElectronegativity Difference

Covalent < 1.67Covalent < 1.67

However –However –0 -.3 is non-polar covalent0 -.3 is non-polar covalent . 3 – 1.67 polar covalent. 3 – 1.67 polar covalentThere are 7 instances of perfectly covalent There are 7 instances of perfectly covalent

bonds (electronegativity difference = 0)bonds (electronegativity difference = 0)HH22, N, N22, O, O22, F, F22, Cl, Cl22, Br, Br22, I, I22

Practice problems 22Practice problems 22

Pg. 266Pg. 266

What is a covalent bond?What is a covalent bond?

Bond that results from the sharing of electons Bond that results from the sharing of electons between nonmetalsbetween nonmetals

Type of bonding found in majority of known Type of bonding found in majority of known compounds compounds

Molecule Molecule – formed when two or more atoms – formed when two or more atoms bond covalentlybond covalently

***Ex. of molecules – carbohydrates, proteins, ***Ex. of molecules – carbohydrates, proteins, fats, DNA, wool, cotton, and synthetic fibers fats, DNA, wool, cotton, and synthetic fibers found in clothes you wear all consist of found in clothes you wear all consist of moleculesmolecules

Lewis structuresLewis structures

Use electron dot diagrams or Lewis dot Use electron dot diagrams or Lewis dot diagrams to show how electrons are diagrams to show how electrons are arranged in moleculesarranged in molecules

Ex. HBrEx. HBrPg. 244 practice problems 19 use different Pg. 244 practice problems 19 use different

colors for different atomscolors for different atoms

Covalent bondsCovalent bonds

Lewis structuresLewis structuresSingle covalent bonds – single pair of Single covalent bonds – single pair of

electrons sharedelectrons sharedDouble covalent bond - sharing of two Double covalent bond - sharing of two

pairs of electronspairs of electronsTriple bond – sharing of 3 pairs of Triple bond – sharing of 3 pairs of

electronselectrons

Nomenclature (naming)Nomenclature (naming)

Covalent bonds are generally between two Covalent bonds are generally between two non-metals.non-metals. COCO COCO22

- Carbon monoxideCarbon monoxide- Carbon dioxideCarbon dioxide

PrefixesPrefixes

11 22 33 44 55 66 77 88 99

- Mon(o)Mon(o)- DiDi- TriTri- Tetr(a)Tetr(a)- Pent(a)Pent(a)- Hex(a)Hex(a)- Hept(a)Hept(a)- OctOct- NonNon

Nitrogen and oxygenNitrogen and oxygen(five molecules)(five molecules)

NN22O O NONO NN22OO33

NONO22

NN22OO55

- Dinitrogen monoxideDinitrogen monoxide- Nitrogen monoxideNitrogen monoxide- Dinitrogen trioxideDinitrogen trioxide- Nitrogen dioxideNitrogen dioxide- Dinitrogen pentoxideDinitrogen pentoxide

Metallic BondsMetallic Bonds

Bonding in metals is due to Bonding in metals is due to delocalized delocalized electrons. electrons.

These often exist in what is called a These often exist in what is called a sea of sea of electrons.electrons.

Metal atomsSea of “delocalized” electrons

Metallic BondsMetallic Bonds

This explains many of the properties of This explains many of the properties of metals:metals:

MalleableMalleableDuctile Ductile Conducts electricity wellConducts electricity well

AlloysAlloys

Two Metals (and sometimes other Two Metals (and sometimes other substances) bonded (mixed) together.substances) bonded (mixed) together.

AlloysAlloys

Two Metals (and sometimes other Two Metals (and sometimes other substances) bonded (mixed) together.substances) bonded (mixed) together.

AlloysAlloys

Two Metals (and sometimes other Two Metals (and sometimes other substances) bonded (mixed) together.substances) bonded (mixed) together.

AlloysAlloys

Two Metals (and sometimes other Two Metals (and sometimes other substances) bonded (mixed) together.substances) bonded (mixed) together.