Cations/Metals/+ve ions

Gp 1 Gp 2 Gp 3 Transition metals ions ( variable oxidation states)

Oxidation state

+1

Oxidation

state

+2

Oxidation state

+3

Sc +3

Ti +2 +3

V +2 +3

Cr +2 +3 +6

Mn +2 +3 +6 +7

Fe +2 +3

Co +2 +3

Ni +2

Cu +1 +2

Zn +2

Li 1+ Be2+ Sc 3+ Ti 2+

Ti 3+

V 2+

V 3+

Cr 2+

C r3+

Cr6+

Mn 2+

Mn 3+

Mn 6+

Mn 7+

Fe 2+

Fe 3+

Co2+

Co 3+

Ni2+ Cu1+

Cu2+

Zn2+

Na 1+ Mg2+ Al 3+

K 1+ Ca2+

Anion/Non metal

Gp 5 Gp 6 Gp 7

Oxidation state

Oxidation state

Oxidation state

-3 -2 -1

N3- O2- F-1

P3- S2- CI-1

Br-1

I-1

Metal/Cations/+ve ions

Non Metal/ Anions/ -ve ions

Ionic Compound

Li2O MgCI2 Al2O3 FeO Iron(II) oxide

NiO Nickel(II) oxide

CuO Copper(II) oxide

Li3N Mg3N2 AlN Fe3N2

Iron(II) nitride Ni3N2

Nickel(II) nitride Cu3N2

Copper(II) nitride

Oxidation state/Charge ion → Li1+ O2-

Formula compound Li2 O1

Video on polyatomic ions

Writing Chemical Formula

Step 1 : Write Oxidation state/charge

Step 2 : Balance it, (electrically neutral)

by cross multiply – as subscript

Polyatomic ions

Group of non-metals bonded together

Oxidation state

Oxidation state

Oxidation state

-1/+1 -2 -3

(OH)-1

Hydroxide (SO4)2-

Sulphate (PO4)3-

Phosphate

(CN)-1

Cyanide (SO3)

2-

Sulphite

(SCN)-1

Thiocyanate (CO3)

2-

Carbonate

(NO3)-1

Nitrate (S2O3)

2-

Thiosulphate

(NO2)-1

Nitrite (Cr2O7)

2-

Dichromate

(NH4)+1

Ammonium

Polyatomic ions

Li2(CO3) Mg(CO3) Al2(CO3)3 Fe(CO3) Ni(CO3) Cu(CO3)

Li(OH) Mg(OH)2 Al(OH)3 Fe(OH)2 Ni(OH)2 Cu(OH)2

Li2(SO4) Mg(SO4) Al2(SO4)3 FeSO4 Ni(SO4) Cu(SO4) Video on polyatomic ions

Ionic Compound

Writing Chemical Formula

Metal/Cations/+ve ions

Cations/Metals/+ve ions

Gp1 Gp 2 Gp3 Transition metals ions ( variable oxidation states)

Oxidation state

+1

Oxidation

state

+2

Oxidation state

+3

Sc +3

Ti +2 +3

V +2 +3

Cr +2 +3 +6

Mn +2 +3 +6 +7

Fe +2 +3

Co +2 +3

Ni +2

Cu +1 +2

Li 1+ Be2+ Sc 3+ Ti 2+

Ti 3+

V 2+

V 3+

Cr 2+

C r3+

Cr6+

Mn 2+

Mn 3+

Mn 6+

Mn 7+

Fe 2+

Fe 3+

Co2+

Co3+

Ni2+ Cu1+

Cu2+

Na 1+ Mg2+ Al 3+

K 1+ Ca2+

Oxidation state/Charge ion → Li1+ (CO3)2-

Formula compound Li2 (CO3)1

Step 1 : Write Oxidation state/charge ion

Step 2 : Balance it, (electrically neutral)

by cross multiply – as subscript

Redox (Oxidation and Reduction)

Oxidation – Gain of oxygen ↑

Oxidation – Loss of hydrogen ↓ Reduction – Gain of hydrogen ↑

Reduction – Loss of oxygen ↓

Oxidation Reduction

Gain oxygen ↑ Loss oxygen ↓

Gain oxidation Number ↑

Loss oxidation Number ↓

Loss hydrogen ↓ Gain hydrogen ↑

Loss electron ↓ Gain electron ↑

Ca + O2 → CaO CH4 + 2O2 → CO2+ 2H2O gain oxygen gain oxygen

Zn + CuO → ZnO + Cu PbO + CO → Pb + CO2

loss oxygen loss oxygen

H2S + CI2 → S +2HCI loss hydrogen

H2S + CI2 → S + 2HCI

Redox - Oxidation state change - Electron transfer

CH4 + 2O2 → CO2 + 2H2O

gain hydrogen

Zn + CuSO4 → ZnSO4 + Cu Zn + CI2 → ZnCI2

No gain/loss oxygen/hydrogen

Redox

gain oxygen

gain hydrogen

Reduction

Oxidation

Are these redox rxns?

Redox - Oxidation state change - Electron transfer

Zn + CuSO4 → ZnSO4 + Cu Zn + CI2 → ZnCI2 No gain/loss

oxygen/hydrogen

Are these redox rxns?

Yes – change in oxidation number

Yes – loss/gain of electron Yes – change in oxidation number

Yes – loss/gain of electron ✓ ✓

• Assuming bond are ionic with diff EN values (unless bet same element)

• Assign each atom, measure of electron control relative to atom in pure element

• Apparent/imaginary charge it has when bonded to diff elements

• Unequal sharing electron based on electronegativity

• + means lose electron

• - means gain electron

Oxidation State/Number/ON Rules

Oxidation Reduction

Gain oxygen ↑ Loss oxygen ↓

Gain oxidation Number ↑

Loss oxidation Number ↓

Loss hydrogen ↓ Gain hydrogen ↑

Loss electron ↓ Gain electron ↑

H CI xx

xx

• x

∂- ∂+

+1 -1 Oxidation number

Oxidation state (sign, number) +2 NOT 2+

Oxidation state and formal charge useful tool for electron book- keeping. They are not REAL!

- Oxidation state -Assume bond ionic with diff EN values (unless bet same element)

- Formal charge – Assume bond covalent

Redox (Oxidation and Reduction)

Redox (Oxidation and Reduction)

• Assuming bond are ionic with diffEN values (unless bet same element)

• Assign each atom, measure of electron control relative to atom in pure element

• Apparent/imaginary charge it has when bonded to diff elements

• Unequal sharing electron based on electronegativity

• + means lose electron

• - means gain electron

Oxidation Number/ON Rules

H CI xx

xx

• x

∂- ∂+

+1 -1 Oxidation number

Oxidation state (sign, number) +2 NOT 2+

Oxidation state and formal charge useful tool for electron book- keeping. They are not REAL!

- Oxidation state -Assume bond ionic with diff EN values (unless bet same element)

- Formal charge – Assume bond covalent

xx

CI CI

Oxidation Number/ON Rules

H CI Na CI

Imagine electron move to more EN element

O C O

oo

o

o

xx oo

oo xx

xx o

x

Equal sharing

xx

xx

xx

o

x

+1 -1 Unequal sharing

0 0

xx

xx

xx

o

x

+1 -1

Complete transfer

ox

ox o

o

oo

oo

oo

oo

o

o

xo

xo

Unequal sharing

-2 +4 -2

H O H

CI2 H CI Na CI C O2

+1 -1 -1 +1 +4 -2

oo

o

x

o

x

+1 -2 +1

Unequal sharing

H N H

H o

x

o

x

o

x

oo

+1 -3 +1

+1

Unequal sharing

H2 O N H3

H C H

H

H

o

x

o

x o

x

o

x

+1

+1

+1

+1 -4

C H4 +1 -2 -3 +1 -4 +1

CI C CI

CI

CI

-1

-1

-1

-1

xx

xx

xx

xx

xx

xx

xx

xx

xx

xx

xx

xx

xo

xo

ox

ox

+4

C CI4 +4 -1

0

Exceptions

Element ON Exception Example

Hydrogen +1 H +1

-1 Bond to metal Metal hydride

NaH CaH2

Oxidation Number/States/ON Rules Imagine electron move to more EN element

• Assuming bond are ionic with diff EN values (unless bet same element)

• Assign each atom, measure of electron control relative to atom in pure element

• Apparent/imaginary charge it has when bonded to diff elements

• Unequal sharing electron based on electronegativity H CI

xx

∂- xx

• x

Oxidation number +1 -1

∂+

xx

H CI

xx

xx

xx

+1 -1

o

x

Unequal sharing

H CI +1 -1

Na H o

x

+1 -1

Complete transfer

Na H +1 -1

Exceptions

Element ON Exception Example

Oxygen -2 O -2

+2

Bond to fluorine

F2O

Exceptions

Element ON Exception Example

Oxygen -2 O -2

-1 Peroxide

(O-O)

H2O2

H O H F O F oo

oo

o

x

o

x

+1 -2 +1 Unequal sharing

H2 O +1 -2

oo

oo

xx

xx

xx

xx

xx

xx

o x

o x

-1 +2 -1 Unequal sharing

F2 O -1 +2

O O H H

O-O single bond

oo

oo

oo

oo

o x

o x

o

o

equal sharing

+1 -1 -1 +1 Unequal sharing

H2 O2

+1 -1

EN fluorine higher ↑ EN oxygen higher ↑

Oxidation Number/ON Rules Imagine electron move to more EN element

O O H O H

Oxidation state O different – depend element bond with – different EN values !

F O F O O xx

xx

xx

xx

xx

xx

Equal sharing

0 0

O2 0

oo

oo

oo

oo

o x

o x

+1 -2 +1

Unequal sharing

H2 O +1 -2

xx

xx

xx xx

xx xx

o x

o x

-1 +2 -1

F2 O -1 +2

H H oo

oo

oo

oo

o

o

o x

o x

+1 -1 -1 +1

H2 O2 +1 -1

Unequal sharing Unequal sharing

Oxidation Number/ON Rules Imagine electron move to more EN element

• Assuming bond are ionic with diff EN values (unless bet same element)

• Assign each atom, measure of electron control relative to atom in pure element

• Apparent/imaginary charge it has when bonded to diff elements

• Unequal sharing electron based on electronegativity H CI

xx

∂- xx

• x

Oxidation number +1 -1

∂+

xx

Oxidation Number/ON Rules Imagine electron move to more EN element

O O H O H Oxidation state O different – depend element bond with – different EN values !

F O F O O xx

xx

xx

xx

xx

xx

Equal sharing

0 0

O2 0

oo

oo

oo

oo

o x

o x

+1 -2 +1

Unequal sharing

H2 O +1 -2

xx

xx

xx xx

xx xx

o x

o x

-1 +2 -1

F2 O -1 +2

H H oo

oo

oo

oo

o

o o

x

o x

+1 -1 -1 +1

H2 O2

+1 -1

Unequal sharing Unequal sharing

Oxidation Number/ON Rules Imagine electron move to more EN element

Oxidation state N different – depend element bond with – different EN values !

H N H

H

H

H O N O H O N O N O N

O

O O

O

o x

o x

o x

x x x x

+1 -3 +1

+1

-2

[N H4 ]

-3 +1 +1

Unequal sharing

xx

o x

o x

xo

xo

xx

oo

oo oo

oo

+1 -2 +3 -2

Unequal sharing

H N O2

+1 +3 -2

O

o x

o x

xo

xo

xx

oo

o

o o

o

+1 -2 +5 -2

-2

Unequal sharing

H N O3

+1 +5 -2

o x

o x

xx

oo

xx

oo

o

o

o

o o

o

o

o

o

o o

o

o

o

o

o

oo oo -2

-2 -2

-5 -5 -2

N2 O5

Unequal sharing

-5 +2

+1 +

Oxidation Number/ON Rules

Atoms uncombined free element state = ON = 0

Ion form – ON same as charged on ion

1

2

Mg

Mg2+

Na

Na+

O2 S8

O2-

3 ON for element same as its most common ion/group ON metal from Gp 1 – 3

ON non metal Gp 5 - 7

Anion/Non metal

Gp 5 Gp 6 Gp 7

Oxidation state

Oxidation state

Oxidation state

- 3 - 2 - 1

N 3- O 2- F 1-

P 3- S 2- CI 1-

Cation/Metal

Gp 1 Gp 2 Gp 3

Oxidation state

Oxidation state

Oxidation state

+1 +2 +3

Na 1+ Mg 2+ Al 3+

K 1+ Ca 2+ Ga 3+

4

CI2 0 0 0 0 0

+1 +2 -2 -1 -2

CI- S2-

ON for transition metal varies Transition metal ions

Transition metals ions (variable oxidation states)

Sc +3

Ti +2 +3

V +2 +3

Cr +2 +3 +6

Mn +2 +3 +6 +7

Fe +2 +3

Co +2 +3

Ni +2

Cu +1 +2

Zn +2

Sc 3+ Ti 2+

Ti 3+

V 2+

V 3+

Cr 2+

Cr 3+

Cr 6+

Mn 2+

Mn 3+

Mn 6+

Mn 7+

Fe 2+

Fe 3+

Co 2+

Co 3+

Ni 2+ Cu 1+

Cu 2+

Zn 2+

Oxidation number

Diff ON Charge on ion

Click here on oxidation rules Click here view simple step

Notes

Sc3+

Charge on Sc

Oxidation

number

+3

Oxidation

state

- + 3+

ON all atoms in polyatomic ion add up to charge of polyatomic ion

ON all atoms in neutral molecule add up to 0

CO3 2- SO4

2-

H2SO4 CO2 5

Oxidation Number/ON Rules

HNO3

(+1)2 + (+6) + (-2)4 = 0

+1 +6 -2

(+4) + (-2)2 = 0 (+1) + (+5) + (-2)3 = 0

+4 -2 +1 +5 -2

(+4) + (-2)3 = -2

+4 -2

(+6) + (-2)4 = -2

NO31-

+6 -2

(+5) + (-2)3 = -1

+5 -2

7 ON atom/molecule of element = 0

(NOT combined)

H2 CI2 O2 Fe Cu Mg

0 0 0 0 0 0

8 Monoatomic ion – ON same as charged on ion

Ionic compound

Charge ion Oxidation number

MgF2 Mg 2+ F 1- Mg (+2) F (-1)

NaCI Na 1+ CI 1- Na (+1) CI (-1)

KBr K 1+ Br 1- K (+1) Br (-1)

CaI2 Ca 2+ I 1- Ca (+2) I (-1)

Li3N Li 1+ N 3- Li (+1) N (-3)

Al2O3 Al 3+ O 2- AI (+3) O (-2)

9 Formula

compound Charge Oxidation

number Name using oxidation

number

FeO Fe 2+ or 2+ +2 Iron (II) oxide

Fe2O3 Fe 3+ or 3+ +3 Iron (III) oxide

Cu2O Cu 1+ or 1+ +1 Copper (I) oxide

CuO Cu 2+ or 2+ +2 Copper (II) oxide

MnO2 Mn 4+ or 4+ +4 Manganese (IV) oxide

MnO4- Mn 7+ or 7+ +7 Manganese (VII) oxide

K2Cr2O7 Cr 6+ or 6+ +6 Potassium dichromate (VI)

Cr2O3 Cr 3+ or 3+ +3 Chromium (III) oxide

Click here view chemguide notes

6

Oxidation Number/ON Rules

9 Metal more than one oxidation states, Roman numeral used

Manganese Chromium

Ionic compound

MnSO4 MnO2 K2MnO4 KMnO4 K2Cr2O7 Cr2O3

Oxidation Number

(+2) + (+6) + (-2)4 = 0

Mn (+2) (+4) + (-2)2 = 0

Mn (+4) (+1)2 + (+6) + (-2)4 = 0

Mn (+6) (+1) + (+7) + (-2)4 = 0

Mn (+7) (+1)2 + (+6)2 + (-2)7 = 0

Cr (VI) (+3)2 + (-2)3 = 0

Cr (III)

IUPAC name

Manganese (II)

sulphate

Manganese (IV)

oxide

Manganese (VI)

Manganese (VII)

Chromium (VI)

Chromium (III)

Iron Copper

Ionic compound

FeCI2 FeCI3 CuCI CuCI2

Oxidation Number

(+2) + (-1)2 = 0

Fe (+2) (+3) + (-1)3 = 0 Fe (+3)

(+1) + (-1) = 0 Cu (+1)

(+2) + (-1)2 = 0 Cu (+2)

IUPAC name

Iron (II) chloride Iron (III) chloride Copper (I) chloride Copper (II) chloride

Vanadium

VO2 + VO 2+

(+5) + (-2)2 = +1

V (+5) (+4) + (-2) = +2

V (+4)

Vanadium (V) Vanadium (IV)

ON for underlined element in ionic compound 10

Na2SO3 Na2SO4 NaNO2 NaNO3 (SO3)2- (SO4)

2-

(+1)2 + (+4) + (-2)3 = 0 (+1)2 + (+6) + (-2)4 = 0 (+1)+ (+3) + (-2)2 = 0 (+1)+ (+5) + (-2)3 = 0 (+4) + (-2)3 = -2 (+6) + (-2)4 = -2

ON for S = +4 ON for S = +6 ON for N = +3 ON for N = +5 ON for S = +4 ON for S = +6

+1 +4 -2 +1 +6 -2 +1 +3 -2 +1 +5 -2 +4 -2 +6 -2

Oxidation Number/ON Rules

11 ON for underlined element in compound

OH-1 PO4

3- S2O32- CN-1 OCI-1 H2O2 (HCO3)

-1

(-2) + (+1) = -1 (+5) + (-2)4 = -3 (+2)2 + (-2)3 = -2 (+4) + (-5) = -1 (-2) + (+1) = -1 (+1)2 + (-1)2 = 0

ON for O = -2 ON for P = +5 ON for S = +2 ON for C = +4 ON for O = -2 ON for O = -1 ON for C = +4

(+1) + (+4) + (-2)3 = -1

-2 +1 +5 -2 +2 -2 +4 -5 -2 +1 +1 -1 +1 +4 -2

Oxidation Reduction

Gain oxygen ↑ Loss oxygen ↓

Loss hydrogen ↓ Gain hydrogen ↑

Redox (Oxidation and Reduction)

Rxn involve gain/loss of oxygen/hydrogen

CH4 + 2O2 → CO2 + 2H2O

Gain hydrogen

Oxygen reduction

gain oxygen

Carbon oxidation

Rxn involve gain/loss of electron

Oxidation Reduction

Gain ON ↑ Loss ON ↓

Loss electron ↓ Gain electron ↑ - broader definition - cover more rxn types

PbO + CO → Pb + CO2

Lead Reduction

gain oxygen

Carbon oxidation

(-4) (+4)

(0) (-2)

ON ↑

ON ↓ oxygen reduced

carbon oxidized

PbO + CO → Pb + CO2

(+2) (0) lead reduced

(+2) (+4)

CH4 + 2O2 → CO2 + 2H2O

ON ↑ carbon oxidized

ON ↓ loss oxygen

Redox (Oxidation and Reduction)

• Assuming bond are ionic with diff EN values (unless bet same element)

• Assign each atom, measure of electron control relative to atom in pure element

• Apparent/imaginary charge it has when bonded to diff elements

• Unequal sharing electron based on electronegativity

Oxidation Number/ON Rules

H CI xx

xx

• x

∂- ∂+

+1 -1 Oxidation number Oxidation state (sign, number) +2 NOT 2+ Oxidation state useful tool for electron book- keeping. They are not REAL! - Oxidation state -Assume bond ionic with diff EN values (unless bet same element)

xx

Na CI

Oxidation Number/ON Rules Imagine electron move to more EN element

xx

xx

xx

o

x

+1 -1 Complete transfer

Na CI +1 -1

Ionic compound

H CI

Covalent compound

xx

xx

+1 -1

xx

o

x

H CI

Unequal sharing

+1 -1

Organic Covalent compound

H C O H

H

H o

x

o

x

o

X

o

X

o

x

oo

-2 +1

+1

+1

+1 -2

C H4 O

Unequal sharing

Still covalent bond

Treat as imaginary ionic (loss/gain of electron control)

Bonds are still covalent NOT ionic, keep track where electron going

-2 +1 -2

(+1) + (-1) = 0 (+1) + (-1) = 0

(-2) + (+1)4 + (-2) = 0

O S O

O

oo

xx oo

xx

oo

xx

-2 +6 -2

-2

S O3

+6 -2

(+6) + (-2)3 = 0 Click here note ON for organic carbon

oo oo

oo

o

o

o

o o

o

ON for carbon

is NOT -2

Oxidation Number/ON Rules

• Assuming bond are ionic with diff EN values (unless bet same element) • Apparent/imaginary charge it has when bonded to diff elements

• Unequal sharing electron based on electronegativity

- Oxidation state useful tool for electron book- keeping. They are not REAL!

Oxidation state (sign, number) +2 NOT 2+

Click here here note ON carbon

H C C H

Oxidation state Carbon compound

-4 CH4

-3 C2H6

-2 CH3CI

-1 C2H2

0 CH2CI2

+1 CHCI2-CHCI2

+2 CHCI3

+3 C2CI6

+4 CCI4

ON carbon (Organic molecules)

Average oxidation number bet carbon is taken!

Different ON states

Don’t need to take average ON bet carbons

Oxidation state

Carbon compound

-3 and -1 CH3CH2OH

-3 and +1 CH3CHO

Different ON states

o

x

o

x

+1 -1 -1 +1

C2 H2

-1 +1

ox

ox

ox

Equal sharing

(-1)2 + (+1)2 = 0

H C C O H

H

H

o

X

o

x

o

X

o

X

oo

o

x

o

x

H

H

o

X oo

o

x

+1

+1

-2

+1

+1

+1

+1 -1 -3

C2 H6 O1

x +1 -2

2x + 6 -2 = 0

x = -2

ON C in CH3 = -3

ON C in CH2 = -1

Average ON C = -2

H C C O

H o

x

+1

H

H

o

X

o

X

o

x

o

X

oo

xo

xo

oo

+1

+1 +1

-3 -2

+1

C2 H4 O1

x +1 -2

2x + 4 -2 = 0

x = -1 ON for carbon

is NOT -1

ON C in CH3 = -3

ON C in CH = +1

Average ON C = -1

ON C in CH3 = -3

ON C in COOH = +1

Average ON C = 0

+3

Oxidation Number/ON Rules

• Assuming bond are ionic with different EN values (unless bet same element) • Apparent/imaginary charge it has when bonded to diff elements

• Unequal sharing electron based on electronegativity

- Oxidation state useful tool for electron book- keeping. They are not REAL!

Oxidation state (sign, number) +2 NOT 2+

Click here here note ON carbon

ON carbon (Organic molecules)

Average oxidation number bet carbon is taken!

Oxidation state carbon

Carbon compound

-3 and +3 CH3COOH

H C C O H

H

H

o

X

o

x

o

X

o

X

oo

o

x

o

x

H

H

o

X oo

o

x

+1

+1

-2

+1

+1

+1

+1 -1

C2 H6 O1

x +1 -2

2x + 6 -2 = 0

x = -2

ON C in CH3 = -3

ON C in CH2 = -1

Average ON C = -2

H C C O

H o

x

+1

H

H

o

X

o

X

o

x

o

X

oo

xo

xo

oo

+1

+1 +1

-3 -2

+1

C2 H4 O1

x +1 -2

2x + 4 -2 = 0

x = -1

ON for carbon

is NOT -2

ON for carbon

is NOT -1

ON C in CH3 = -3

ON C in CH = +1

Average ON C = -1

H C C O H

H O

H

+1

o

x

o

X

+1

+1

o

X -3 -3

o

x

+1

oo

oo

oo

oo

xx

o

o

o

x

o

x

-2

ON for carbon

is NOT 0

C2 H4 O2

x +1 -2

2x + 4 -4 = 0

x = 0

Oxidation state carbon

Carbon compound

-3 and -1 CH3CH2OH

Oxidation state carbon

Carbon compound

-3 and +1 CH3CHO

NOT Redox rxn • NO Loss/gain electron

• NO change in oxidation number

Concept Map

Type of chemical reaction

Combustion/Respiration rxn Displacement rxn

Synthesis rxn Decomposition rxn

Single Displacement

Double Displacement

Acid/Base rxn

Involve oxygen!!

CH4 + 2O2 → CO2+ 2H2O C6H12O6 +6O2 → 6CO2+6H2O

Redox rxn • Loss/gain electron

• Change in oxidation number

Zn + 2HCI→ H2+ ZnCI2 Zn + CuO → ZnO + Cu

Redox rxn • Loss/gain electron

• Change in oxidation number

KI + Pb(NO3)2 → PbI2 + KNO3

Type of chemical reaction

HCI + NaOH → NaCI + H2O MgO + 2HCI → MgCI2 + H2O 2H2 + O2 → 2H2O 2KCIO3 → 2KCI + 3O2

Redox rxn • Loss/gain electron

• Change in oxidation number

Redox rxn • Loss/gain electron

• Change in oxidation number

NOT Redox rxn • NO Loss/gain electron

• NO change in oxidation number

H CI + Na O H → NaCI + H2 O +1 -1 +1 -2 +1 +1 -1 +1 -2

2H2 + O2 → 2H2O 0 0 +1 -2

2K CI O3 → 2K CI + 3O2 +1 +5 -2 +1 -1 0

C6 H12 O6 + 6O2 → 6C O2 + 6H2 O Zn + 2H CI → H2 + Zn CI2 0 +1 -1 0 +2 -1

K I + Pb (N O3)2 → Pb I2 + K N O3

+1 -1 +2 +5 -2 +2 -1 +1 +5 -2 0 +1 -2 0 +4 -2 +1 -2

Oxidation state

Carbon compound

-4 CH4

-3 C2H6

-2 CH3CI

-1 C2H2

0 CH2CI2

+1 CHCI2-CHCI2

+2 CHCI3

+3 C2CI6

+4 CCI4

Different ON/ states for Carbon Different ON/ states for sulphur

Carbon attach to H – ON lower ↓ - Carbon less oxidized - Carbon attract electron

Carbon attach to CI/O (EN ↑) – ON higher ↑ - Carbon more oxidized - Carbon lose electron

Oxidation state

Sulphur compound

-2 H4S

0 S8

+2 SCI3

+4 SO2

+4 SO3 2-

+6 SO3

+6 H2SO4

Sulphur attach to H /CI – ON lower ↓ - Sulphur less oxidized - Sulphur attract electron

Sulphur attach to O (EN ↑) – ON higher ↑ - Sulphur more oxidized - Sulphur lose electron

Oxidation numbers and name

Formula ion

Charge Oxidation number

Name using ON

CrO42- 2- ON for Cr +6 Chromate (VI)

Cr2O7 2- 2- ON for Cr +6 Dichromate (VI)

MnO4- 1- ON for Mn +7 Manganate (VII)

MnO42- 2- ON for Mn +6 Manganate (VI)

CIO - 1- ON for CI +1 Chlorate (I)

CIO3 - 1- ON for CI +5 Chlorate (V)

CIO2 - 1- ON for CI +3 Chlorate (III)

CIO4 - 1- ON for CI +7 Chlorate (VII)

Formula compound

Charge Oxidation number

Name using oxidation number

FeO Fe 2+ or 2+ +2 Iron (II) oxide

Fe2O3 Fe 3+ or 3+ +3 Iron (III) oxide

Cu2O Cu 1+ or 1+ +1 Copper (I) oxide

CuO Cu 2+ or 2+ +2 Copper (II) oxide

MnO2 Mn 4+ or 4+ +4 Manganese (IV) oxide

MnO4- Mn 7+ or 7+ +7 Manganese (VII) oxide

K2Cr2O7 Cr 6+ or 6+ +6 Potassium dichromate (VI)

Cr2O3 Cr 3+ or 3+ +3 Chromium (III) oxide

Period 2

Shared electron cloud closer to O

Electronegativity

Electronegativity (EN) •Tendency of atom to attract/pull shared/bonding electron to itself •EN value higher – pull/attract electron higher (EN value from 0.7 – 4)

EN highest EN lowest

Factors affecting EN value •Size of atom/distance – small size/distance – stronger attraction for electron •Nuclear charge – higher nuclear charge – stronger attraction for electron

Electronegativity •EN increase up a Group •EN increase across a Period

F

CI

Br

I

Size increase

Attraction electron decrease

EN lower

Size

Be

+4

Li

+3 B

+5 N

+7

O

+8 F

+9

EN increase across period 2

Nuclear charge

EN increase across period 2 Nuclear charge increase Strong attraction for electron

EN increase

Gp 17

C

+6

EN decrease down gp 17

FORMAL CHARGE (FC)

Tool/Model for comparing which Lewis structures is more acceptable

Lewis structure SO2

Which is acceptable?

Lewis structure SO3

Formal Charge •Treats covalent bond with equal electron distribution no EN diff bet atom •Electronegative atom has negative while least electronegative atom has positive formal charge.

Formula formal charge

Click here video formal charges Click here video formal charges

V - valence electrons of atom

L – Lone pair electron

B - electrons shared in covalent bonds in the molecule

✓ ✓

All resonance structure contribute to electronic structure. Real structure is combination of them. Lowest formal charge (stable), contribute more than less stable structure. Sum of formal charges must be zero for neutral or equal to charge on ion.

L +

Formal charge concept

Formal charge NOT real !!