Ch. 13: Chemical Ch. 13: Chemical Formulas and Formulas and

NamesNames13.3 Oxidation States13.3 Oxidation States

Oxidation StatesOxidation States Also called oxidation numbersAlso called oxidation numbers For an individual atom of one typeFor an individual atom of one type Used to indicate approximate electron Used to indicate approximate electron

distribution in distribution in covalent bondingcovalent bonding What contains covalent bonding?What contains covalent bonding?

molecular compounds molecular compounds polyatomic ionspolyatomic ions

Not “real” charges since electrons are Not “real” charges since electrons are sharedshared

Oxidation StatesOxidation States

Shared electron are counted as Shared electron are counted as “belonging” to the “belonging” to the moremore electronegative elementelectronegative element Since it has a greater attraction for Since it has a greater attraction for

the electronsthe electrons The electrons are actually located The electrons are actually located

closer to that atomcloser to that atom Periodic Trend for Periodic Trend for

electronegativity: increases as you electronegativity: increases as you go up and to the rightgo up and to the right

Assigning Oxidation Assigning Oxidation StatesStates

Atoms in a pure element have an Atoms in a pure element have an oxidation state of zero.oxidation state of zero. Na, ONa, O22, Fe, etc., Fe, etc.

The more electronegative element is The more electronegative element is assigned a assigned a negative negative oxidation state oxidation state while the less electronegative has a while the less electronegative has a positive statepositive state CFCF44: :

C is less electronegative: +C is less electronegative: + F is more electronegative: -F is more electronegative: -

Assigning Oxidation Assigning Oxidation StatesStates

FluorineFluorine always has a -1 oxidation always has a -1 oxidation statestate Since it is the most electronegative Since it is the most electronegative

elementelement OxygenOxygen usually has a -2 usually has a -2

Except in peroxides where it has a -1Except in peroxides where it has a -1 HydrogenHydrogen usually has a +1 usually has a +1

But when it is paired with a metal, it But when it is paired with a metal, it has a -1: ex. LiHhas a -1: ex. LiH

Assigning Oxidation Assigning Oxidation StatesStates

Sum of the oxidation states must equal Sum of the oxidation states must equal zero in a neutral compoundzero in a neutral compound NN22OO55

O: -2 x 5 = -10O: -2 x 5 = -10 N: +5 x 2 = +10N: +5 x 2 = +10

Sum of states in a Sum of states in a monatomic/polyatomic ion must equal monatomic/polyatomic ion must equal the charge of the ionthe charge of the ion NONO33

--

O: -2 x 3 = -6O: -2 x 3 = -6 N: + 5 x 1 = +5N: + 5 x 1 = +5

Practice Practice UFUF66

F: F: -1-1 0 overall0 overall U: U: +6+6 to balance to balance

6x-16x-1 HH22SOSO44

H: H: +1+1 OO: -2: -2 0 overall0 overall S: S: +6+6 to balance to balance

(4x-2)+(2x+1)(4x-2)+(2x+1)

ClOClO331-1-

O: O: -2-2 -1 overall-1 overall Cl: Cl: +5+5 to balance to balance

3x-2 3x-2 COCO22

O: O: -2-2 0 overall0 overall C: C: +4+4

Determine the Oxidation Determine the Oxidation StatesStates

BrBr22

Br: 0Br: 0 NHNH33

H: H: +1+1 NN: -3: -3

CaSOCaSO33:: Ca:Ca: +2 +2 O:O: -2 -2 S:S: +4 +4

HSOHSO33--

H: H: +1+1 O: O: -2-2 -1 overall-1 overall S: S: +4+4

BB22HH66

H: H: +1+1 0 overall0 overall B: B: -3-3

Using Oxidation States in Using Oxidation States in NamingNaming

Can use Stock System (Roman Can use Stock System (Roman Numerals) to name molecular Numerals) to name molecular compounds toocompounds too

The Roman Numeral in between The Roman Numeral in between names is the oxidation state of the names is the oxidation state of the firstfirst element element

Do NOT simplify the ratio for Do NOT simplify the ratio for molecular compoundsmolecular compounds

Only use either prefixes OR Roman Only use either prefixes OR Roman Numerals, not a combinationNumerals, not a combination

Stock System NamingStock System Naming

PClPCl33 Cl: -1, P: +3Cl: -1, P: +3 Phosphorus (III) chloridePhosphorus (III) chloride

PClPCl55 Cl: -1, P: +5Cl: -1, P: +5 Phosphorus (V) chloridePhosphorus (V) chloride

NN22OO O: -2, N: +1O: -2, N: +1 Nitrogen (I) oxideNitrogen (I) oxide

Stock System NamingStock System Naming

COCO O: -2, C: +2O: -2, C: +2 Carbon (II) oxideCarbon (II) oxide

BrFBrF55 F: -1, Br: +5F: -1, Br: +5 Bromine (V) fluorideBromine (V) fluoride

COCO22 O: -2, C: +4O: -2, C: +4 Carbon (IV) oxideCarbon (IV) oxide

Writing FormulasWriting Formulas Nitrogen (II) oxideNitrogen (II) oxide

N: +2N: +2 O: -2O: -2 NONO

Lead (IV) oxideLead (IV) oxide Pb: +4Pb: +4 O: -2O: -2 PbPb22OO44

PbOPbO22

Sulfur (IV) fluorideSulfur (IV) fluoride S: +4S: +4 F: -1F: -1 SFSF44

Chlorine (III) Chlorine (III) fluoridefluoride Cl: +3Cl: +3 F: -1F: -1 ClFClF33

Writing FormulasWriting Formulas Phosphorus (V) oxidePhosphorus (V) oxide

P: +5P: +5 O: -2O: -2 PP22OO55

Boron (III) hydrideBoron (III) hydride B: +3B: +3 H: -1H: -1 BHBH33

Hydrogen (I) oxideHydrogen (I) oxide H: +1H: +1 O: -2O: -2 HH22OO

carbon (IV) sulfidecarbon (IV) sulfide C: +4C: +4 S: -2S: -2 CSCS22

HomeworkHomework

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