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

Bonds and ElectronegativityBonds and Electronegativity

Electrons are transferred between atoms Electrons are transferred 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.

Electronegativity DifferenceElectronegativity Difference

Covalent < 1.67Covalent < 1.67

However –However –0 -.6 is non-polar covalent0 -.6 is non-polar covalent . 6 – 1.67 polar covalent. 6 – 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

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

Organic MoleculesOrganic Molecules(hydrocarbons)(hydrocarbons)

Composed primarily of carbons (always) Composed primarily of carbons (always) and hydrogens (usually).and hydrogens (usually).

Three primary typesThree primary typesAlkanes – only single bondsAlkanes – only single bondsAlkenes – at least one double bondAlkenes – at least one double bondAlkynes – at least one triple bondAlkynes – at least one triple bond

Root name from # of CarbonsRoot name from # of Carbons 1 – meth1 – meth 2 – eth2 – eth 3 – prop3 – prop 4 – but4 – but 5 – pent5 – pent 6 – hex6 – hex 7 – hept7 – hept 8 – oct 8 – oct 9 – non9 – non 10 - dec10 - dec

Some examplesSome examplesH

H-C-H

H

C- C- C- C--

C- C- C--

H-C- C-

H H

H

H H

methane

ethane

Propane

butane

CH4

C2H6

C3H8

C4H10

Notice: # of H is 2n+2

# of carbons

AlkenesAlkenes

H-C- C-

H H

H

H H

ethane

ethene

# of H’s is just 2n

H H

H-C=C-H

Saturated vs. UnsaturatedSaturated vs. Unsaturated

H-C-C-C-C-C-C-C-C-C-Hɩ ɩ ɩ ɩ ɩ ɩ ɩ ɩ ɩ

ɩɩɩɩɩɩ ɩ ɩ ɩ

H H H H H H H H H

H H H H H H H H H H H H H H H H

H-C-C=C-C-C-C-C-C-C-Hɩ ɩ ɩ ɩ ɩ ɩ ɩ ɩ ɩ

ɩɩɩɩ

H H H H H H H H H

ɩ ɩ ɩ

H-C-C-C=C-C-C-C=C-C-Hɩ ɩ ɩ ɩ ɩ ɩ ɩ ɩ ɩ

ɩɩɩɩɩ H H H H H

H H H H H H H H H

nonane 2-nonene

2,6 nonadiene

Formula MassFormula MassMass of one formula unit.Mass of one formula unit.Add the mass of all of the elements times Add the mass of all of the elements times

their subscripts.their subscripts.Sodium phosphate:Sodium phosphate:NaNa33POPO44

Na = 22.99 x 3 = 68.97 amuNa = 22.99 x 3 = 68.97 amuP = 30.97 x1 = 30.97 amuP = 30.97 x1 = 30.97 amuO = 16.00 x 4 = 64.00 amuO = 16.00 x 4 = 64.00 amu68.97 + 30.97 + 64 = 163.94 amu68.97 + 30.97 + 64 = 163.94 amu

Percent CompositionPercent Composition

What is the percent of sodium in sodium What is the percent of sodium in sodium phosphate?phosphate?

What is the mass of sodium in NaWhat is the mass of sodium in Na33POPO44?? Na = 22.99 x 3 = 68.97 amuNa = 22.99 x 3 = 68.97 amu What is the mass of NaWhat is the mass of Na33POPO44?? 163.94 amu163.94 amu % of Na is 68.97/163.94 x 100 or% of Na is 68.97/163.94 x 100 or 40.07%40.07%

Empirical FormulasEmpirical Formulas

A formula in lowest terms. (Use the GCF)A formula in lowest terms. (Use the GCF)Greatest Common FactorGreatest Common FactorThe empirical formula for CThe empirical formula for C22HH66 is is

CHCH33

What is the formula mass for CWhat is the formula mass for C22HH66??

What is the formula mass for CHWhat is the formula mass for CH33??What is 30 What is 30 ÷÷ 15? 15?

Determining Empirical Formula Determining Empirical Formula from Percent composition.from Percent composition.

A certain compound contains 32.38% A certain compound contains 32.38% sodium, 22.65% sulfur, and 44.99% sodium, 22.65% sulfur, and 44.99% oxygen. Find the empirical formula.oxygen. Find the empirical formula.

We’re going to do percent composition in We’re going to do percent composition in reverse…reverse…

Assume a 100g sample – therefore 32.38g Assume a 100g sample – therefore 32.38g of sodium etc.of sodium etc.

These are the subscripts

Smallest value

Divide all values by the smallest of them(this will give whole numbers)

Determine the molar ratiosDetermine the molar ratios

So, the empirical formula is NaSo, the empirical formula is Na22SOSO44

Na

S

O

32.28g 1 mole22.99g

22.65g 1 mole32.07g

44.99g 1 mole16.0g

= 1.408 moles

= 0.7063 moles

= 2.812moles

0.7063

0.7063

0.7063

= 2

= 1

= 4

Actual Formula from Empirical Actual Formula from Empirical FormulaFormula

If you know the empirical formula and the If you know the empirical formula and the formula mass of the actual formula, you formula mass of the actual formula, you can determine actual formula by finding can determine actual formula by finding the formula mass of the empirical formula the formula mass of the empirical formula and dividing it into the formula mass of the and dividing it into the formula mass of the actual formula. This will give you the actual formula. This will give you the GCF.GCF.

Multiply the subscripts of the empirical Multiply the subscripts of the empirical formula by the GCF.formula by the GCF.

ExampleExample

What is the formula of a compound whose What is the formula of a compound whose molecular mass is 150.1amu and its molecular mass is 150.1amu and its empirical formula is CHempirical formula is CH22O?O?

Formula mass of CHFormula mass of CH22O is 30.02amu.O is 30.02amu.150.1 150.1 ÷÷ 30.02 = 5 (That’s the GCF) 30.02 = 5 (That’s the GCF)Multiply the subscripts 1,2,1 by the GCF Multiply the subscripts 1,2,1 by the GCF

(5) which gives the new subscripts of (5) which gives the new subscripts of 5,10,5 or 5,10,5 or

CC55HH1010OO55

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.