Bonding

Ions

IonsIonsIonsIons• CationCation: A positive ion: A positive ion

• MgMg2+2+, NH, NH44++

• AnionAnion: A negative ion: A negative ion

• ClCl, SO, SO4422

• Ionic BondingIonic Bonding: Force of : Force of attraction between oppositely attraction between oppositely charged ions.charged ions.

Octet rule:atoms tend to combine in such a

way that they each have eight electrons in their valence energy level

• An element's valence energy level is full and most stable when it contains eight electrons

Predicting Ionic ChargesPredicting Ionic Charges

Group 1Group 1::Lose 1 electron to form Lose 1 electron to form 1+1+ ions ions

HH++ LiLi++ NaNa++ KK++

Predicting Ionic ChargesPredicting Ionic Charges

Group 2Group 2::Loses 2 electrons to form Loses 2 electrons to form 2+2+ ions ions

BeBe2+2+ MgMg2+2+ CaCa2+2+ SrSr2+2+ BaBa2+2+

Predicting Ionic ChargesPredicting Ionic ChargesGroup 13Group 13:: Loses 3 Loses 3 electrons to electrons to form form 3+3+ ions ions

BB3+3+ AlAl3+3+ GaGa3+3+

Predicting Ionic ChargesPredicting Ionic ChargesGroup 14Group 14:: Lose 4 Lose 4 electrons or electrons or gain gain 4 electrons?4 electrons?

Neither! Neither! Group 13 Group 13 elements rarely elements rarely form ions.form ions.

Predicting Ionic ChargesPredicting Ionic ChargesGroup 15Group 15:: Gains 3 Gains 3 electrons to electrons to form form 3-3- ions ions

NN3-3-

PP3-3-

AsAs3-3-

Nitride

Phosphide

Arsenide

Predicting Ionic ChargesPredicting Ionic ChargesGroup 16Group 16:: Gains 2 Gains 2 electrons to electrons to form form 2-2- ions ions

OO2-2-

SS2-2-

SeSe2-2-

Oxide

Sulfide

Selenide

Predicting Ionic ChargesPredicting Ionic ChargesGroup 17Group 17:: Gains 1 Gains 1 electron to form electron to form 1-1- ions ions

FF1-1-

ClCl1-1-

BrBr1-1-Fluoride

Chloride

Bromide

II1-1- Iodide

Predicting Ionic ChargesPredicting Ionic ChargesGroup 18Group 18:: Stable Noble Stable Noble gases gases do notdo not form ions!form ions!

Predicting Ionic ChargesPredicting Ionic ChargesGroups 3 - Groups 3 - 1212::

Many Many transitiontransition elements elements have more than one possible have more than one possible oxidation state.oxidation state.Iron(II) = Fe2+ Iron(III) = Fe3+

Predicting Ionic ChargesPredicting Ionic ChargesGroups 3 - Groups 3 - 1212::

Some Some transitiontransition elements elements have only one possible oxidation have only one possible oxidation state.state.Zinc = Zn2+ Silver = Ag+

http://www.wisc-online.com/objects/ViewObject.aspx?ID=GCH2204

Writing Ionic Compound Writing Ionic Compound FormulasFormulas

Example: Aluminum sulfide

1. Write the formulas for the cation and anion, including CHARGES!

AlAl3+3+ SS2-2-2. Check to see if charges are balanced.

3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.

Not balanced!

22 33

Writing Ionic Compound Writing Ionic Compound FormulasFormulas

Example: Iron(III) chloride

1. Write the formulas for the cation and anion, including CHARGES!

FeFe3+3+ClCl--2. Check to see if charges are balanced.

3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.

Not balanced!

33

Writing Ionic Compound Writing Ionic Compound FormulasFormulas

Example: Ammonium sulfate

1. Write the formulas for the cation and anion, including CHARGES!

NHNH44++ SOSO44

2-2-2. Check to see if charges are balanced.

3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.

Not balanced!

( ( ) )

22

Writing Ionic Compound Writing Ionic Compound FormulasFormulas

Example: Barium nitrate

1. Write the formulas for the cation and anion, including CHARGES!

BaBa2+2+ NONO33--2. Check to see if charges

are balanced.

3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.

Not balanced!

( ( ) )

22

Writing Ionic Compound Writing Ionic Compound FormulasFormulas

Example: Magnesium carbonate

1. Write the formulas for the cation and anion, including CHARGES!

MgMg2+2+ COCO332-2-2. Check to see if

charges are balanced.

They are balanced!

Writing Ionic Compound Writing Ionic Compound FormulasFormulas

Example: Zinc hydroxide

1. Write the formulas for the cation and anion, including CHARGES!

ZnZn2+2+ OHOH--2. Check to see if charges are balanced.

3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.

Not balanced!

( ( ))

22

Writing Ionic Compound Writing Ionic Compound FormulasFormulas

Example: Aluminum phosphate

1. Write the formulas for the cation and anion, including CHARGES!

AlAl3+3+ POPO443-3-2. Check to see if charges

are balanced.

They ARE balanced!

Naming Ionic CompoundsNaming Ionic CompoundsNaming Ionic CompoundsNaming Ionic Compounds• 1. 1. Cation first, then anionCation first, then anion

• 2. Monatomic cation = name of 2. Monatomic cation = name of the elementthe element

• CaCa2+2+ = calcium = calcium ionion

• 3. Monatomic anion = 3. Monatomic anion = rootroot + + -ide-ide

• ClCl = chlor = chlorideide

• CaClCaCl22 = calcium chlor= calcium chlorideide

Naming Ionic CompoundsNaming Ionic Compounds(continued)(continued)

Naming Ionic CompoundsNaming Ionic Compounds(continued)(continued)

• -- some some metal forms more than one metal forms more than one cationcation

• -- use use Roman numeralRoman numeral in namein name

• PbClPbCl22

• PbPb2+2+ is cationis cation

• PbClPbCl22 = lead( = lead(IIII) chloride) chloride

Metals with multiple oxidation Metals with multiple oxidation statesstates

Naming Binary CompoundsNaming Binary CompoundsNaming Binary CompoundsNaming Binary Compounds• -- Compounds between two Compounds between two nonmetalsnonmetals• -- First element First element in the formula is in the formula is named firstnamed first..• -- Second element Second element is named as if it were an is named as if it were an

anionanion..• -- Use prefixesUse prefixes• -- Only use Only use monomono on second element - on second element -

PP22OO55 ==COCO22 = =

CO =CO =

NN22O =O =

didiphosphorus phosphorus pentpentoxideoxide

carbon carbon didioxideoxide

carbon carbon monmonoxideoxide

didinitrogen nitrogen monmonoxideoxide

Calculating Formula MassCalculating Formula MassCalculate the formula mass of magnesium Calculate the formula mass of magnesium carbonate, MgCOcarbonate, MgCO33..

24.31 g + 12.01 g + 3(16.00 24.31 g + 12.01 g + 3(16.00 g) =g) =

84.32 g84.32 g

Calculating Percentage Calculating Percentage CompositionComposition

Calculate the percentage composition of Calculate the percentage composition of magnesium carbonate, MgCOmagnesium carbonate, MgCO33..

From previous slide:From previous slide:24.31 g + 12.01 g + 3(16.00 g) = 24.31 g + 12.01 g + 3(16.00 g) = 84.32 g84.32 g 24.31

100 28.83%84.32

Mg 12.01

100 14.24%84.32

C 48.00

100 56.93%84.32

O

100.00

FormulasFormulas

molecular formula = (empirical molecular formula = (empirical formula)formula)nn [ [nn = integer] = integer]

molecular formula = Cmolecular formula = C66HH66 = (CH) = (CH)66

empirical formula = CHempirical formula = CH

Empirical formula: the lowest whole number ratio of atoms in a compound.

Molecular formula: the true number of atoms of each element in the formula of a compound.

FormulasFormulas (continued)(continued)

Formulas for Formulas for ionic compoundsionic compounds are are ALWAYSALWAYS empirical (lowest whole empirical (lowest whole number ratio).number ratio).Examples:Examples:

NaCl MgCl2 Al2(SO4)3 K2CO3

FormulasFormulas (continued)(continued)

Formulas for Formulas for molecular compoundsmolecular compounds MIGHTMIGHT be empirical (lowest whole be empirical (lowest whole number ratio).number ratio).

Molecular:Molecular:

H2O

C6H12O6 C12H22O11

Empirical:

H2O

CH2O C12H22O11

Empirical Formula Empirical Formula DeterminationDetermination

1.1. Base calculation on 100 grams of Base calculation on 100 grams of compound. compound.

2.2. Determine moles of each element in 100 Determine moles of each element in 100 grams of compound.grams of compound.

3.3. Divide each value of moles by the Divide each value of moles by the smallest of the values.smallest of the values.

4.4. Multiply each number by an integer to Multiply each number by an integer to obtain all whole numbers.obtain all whole numbers.

Empirical Formula Empirical Formula DeterminationDetermination

Adipic acid contains 49.32% C, 43.84% O, and 6.85% H by mass. What is the empirical formula of adipic acid?

49.32 14.107

12.01

g C mol Cmol C

g C

6.85 16.78

1.01

g H mol Hmol H

g H

43.84 12.74

16.00

g O mol Omol O

g O

Empirical Formula Empirical Formula DeterminationDetermination

(part 2)(part 2)

4.1071.50

2.74

mol C

mol O

6.782.47

2.74

mol H

mol O

2.741.00

2.74

mol O

mol O

Divide each value of moles by the Divide each value of moles by the smallest of the values.smallest of the values.

Carbon:Carbon:

Hydrogen:Hydrogen:

Oxygen:Oxygen:

Empirical Formula Empirical Formula DeterminationDetermination

(part 3)(part 3)Multiply each number by an integer to Multiply each number by an integer to obtain all whole numbers.obtain all whole numbers.

Carbon: 1.50Carbon: 1.50 Hydrogen: 2.50Hydrogen: 2.50 Oxygen: 1.00Oxygen: 1.00x 2 x 2 x 2

33 55 22

Empirical formula:C3H5O2

Finding the Molecular Finding the Molecular FormulaFormula

The empirical formula for adipic The empirical formula for adipic acid is Cacid is C33HH55OO22. The molecular mass of . The molecular mass of adipic acid is 146 g/mol. What is adipic acid is 146 g/mol. What is the molecular formula of adipic the molecular formula of adipic acid?acid?1. Find the formula mass of 1. Find the formula mass of CC33HH55OO22

3(12.01 g) + 5(1.01) + 2(16.00) = 3(12.01 g) + 5(1.01) + 2(16.00) = 73.08 g73.08 g

Finding the Molecular Finding the Molecular FormulaFormula

The empirical formula for adipic The empirical formula for adipic acid is Cacid is C33HH55OO22. The molecular mass of . The molecular mass of adipic acid is 146 g/mol. What is adipic acid is 146 g/mol. What is the molecular formula of adipic the molecular formula of adipic acid?acid?

3(12.01 g) + 5(1.01) + 2(16.00) = 3(12.01 g) + 5(1.01) + 2(16.00) = 73.08 g73.08 g

2. Divide the molecular mass by 2. Divide the molecular mass by the mass given by the emipirical the mass given by the emipirical formula.formula.

1462

73

Finding the Molecular Finding the Molecular FormulaFormula

The empirical formula for adipic The empirical formula for adipic acid is Cacid is C33HH55OO22. The molecular mass of . The molecular mass of adipic acid is 146 g/mol. What is adipic acid is 146 g/mol. What is the molecular formula of adipic the molecular formula of adipic acid?acid?

3(12.01 g) + 5(1.01) + 2(16.00) = 3(12.01 g) + 5(1.01) + 2(16.00) = 73.08 g73.08 g146

273

3. Multiply the empirical formula 3. Multiply the empirical formula by this number to get the by this number to get the molecular formula.molecular formula.

(C(C33HH55OO22) x 2 ) x 2 ==

CC66HH1010OO44