1

E3 Redox: Transferring electrons

Session one of two• First hour: Discussion (E1)• 2nd and 3rd hour: Lab (E3, Parts 1 and 2A)

Oxidation-Reduction (Redox)

Example: 2 Na(s) + Cl2 (g) → 2 NaCl(s)

Reactions involve electron transfer. Change in charge (oxidation state) of reactants.

Gain of e’s = reduction (Cl → Cl- in NaCl)Lose of e’s = oxidation

(Na → Na+ in NaCl)

Loss of electrons (LEO) = oxidation Gain of electrons (GER) = reduction

Redox reaction

2 Na + Cl2 → 2 ΝaCl + energy

DEMO

LEO GER

2

2 Na + Cl2 → 2 Na + + 2 Cl-

Oxidation Reduction

2 ( ) ( )

( > in oxidation state) ( < in oxidation state)

Na → Na+ + e- Cl2 + 2e- → 2Cl-

Half reactions always written to show electron GAIN.

The final equation reflects the sum of the balanced halfreactions so that electrons lost = electrons gained:

REDOX Half ReactionsOXIDIZING AGENT REDUCING AGENT

Gains electronsand is reduced (GER) and is oxidized (LEO)

Loses electrons

An oxidizing agent brings about the oxidation of another substance.A reducing agent bring about the reduction of another substance.

Redox Agents

2 Na + Cl2 → 2 Νa+ + 2 Cl- + energyRA OA

Q. Identify the reducing agents (RA) and oxidizingagents (OA) in the reaction:

OA RA_________________________________________

1A VIIIA1H

1s1 IIA IIIA IVA VA VIA VIIA

2He1s2

3Li

2s1

4Be

2s2

5B

2s22p1

6C

2s22p2

7N

2s22p3

8O

2s22p4

9F

2s22p5

1 0Ne

2s22p6

1 1Na

3s1

1 2Mg

3s2 IIIB IVB VB VIB VIIBVIIIB !VIIIB IB IIB

1 3Al

3s23p1

1 4Si

3s23p2

1 5P

3s23p3

1 6S

3s23p4

1 7Cl

3s23p5

1 8Ar

3s23p6

1 9K

4s1

2 0Ca

4s2

2 1Sc

3d14s2

2 2Ti

3d24s2

2 3V

3d34s2

2 4Cr

3d54s1

2 5Mn

3d54s2

2 6Fe

3d64s2

2 7Co

3d74s2

2 8Ni

3d84s2

2 9Cu

3d1 04s1

3 0Zn

3d1 04s2

3 1Ga

4s24p1

3 2Ge

4s24p2

3 3As

4s24p3

3 4Se

4s24p4

3 5Br

4s24p5

3 6Kr

4s24p6

3 7Rb

5s1

3 8Sr

5s2

3 9Y

4d15s2

4 0Zr

4d25s2

4 1Nb

4d35s2

4 2Mo

4d55s1

4 3Tc

4d55s2

4 4Ru

4d75s1

4 5Rh

4d85s1

4 6Pd

4d10

4 7Ag

4d1 05s1

4 8Cd

4d1 05s2

4 9In

5s25p1

5 0Sn

5s25p2

5 1Sb

5s25p3

5 2Te

5s25p4

5 3I

5s25p5

5 4Xe

5s25p6

5 5Cs

6s1

5 6Ba

6s2

5 7

La*

5d16s2

7 2Hf

5d26s2

7 3Ta

5d36s2

7 4W

5d46s2

7 5Re

5d56s2

7 6Os

5d66s2

7 7Ir

5d76s2

7 8Pt

5d96s1

7 9Au

5d1 06s1

8 0Hg

5d1 06s2

8 1Tl

6s26p1

8 2Pb

6s26p2

8 3Bi

6s26p3

8 4Po

6s26p4

8 5At

6s26p5

8 6Rn

6s26p6

8 7Fr

7s1

8 8Ra

7s2

8 9Ac#

6d17s2

1 0 4 +

6d27s2

1 0 5 +

6d37s2

1 0 6 +

6d47s2

1 0 7 +

6d57s2

1 0 8 +

6d67s2

1 0 9 +

6d77s2

+ Element synthesized,

but no official name assigned

Oxidation State versus Family Number

Metals lose electrons Non-metals gain electrons

3

11A

18VIIIA

2IIA

- 513

IIIA

- 414

IVA

- 315

VA

- 216

VIA

-117

VIIA

2

He

1s2

5

B

2s22p1

6

C

2s22p2

7

N

2s22p3

8

O

2s22p4

9

F

2s22p5

1 0

Ne

2s22p6

3 IIIB

4 IVB

5 VB

6VIB

7VIIB

8VIIIB

9 !

10 VIIIB

11 IB

12 IIB

1 4

Si

3s23p2

1 5

P

3s23p3

1 6

S

3s23p4

1 7

Cl

3s23p5

1 8

Ar

3s23p6

3 3

As

4s24p3

3 4

Se

4s24p4

3 5

Br

4s24p5

3 6

Kr

4s24p6

5 2

Te

5s25p4

5 3

I

5s25p5

5 4

Xe

5s25p6

8 5

At

6s26p5

8 6

Rn

6s26p6

+ Element synthesized,

but no official name assigned

Nonmetals gain electrons and reduce (GER)+ 1 1

1A

+3

+4

+5

+6

18 VIIIA

1 H

1s1

+2 2

IIA

+1 13

IIIA

+2 14

IVA

+3 15

VA

+4 16

VIA

17 V I I A

3 Li

2s1

4 Be

2s2

1 1 Na

3s1

1 2 Mg

3s2

3

IIIB

4

IVB

5

VB

6

VIB

7

VIIB

8 VI I IB

9 !

10 VIIIB

11

IB

12

IIB

1 3 Al

3s23p1

1 9 K

4s1

2 0 Ca

4s2

2 1 Sc

4s23d1

2 2 Ti

4s23d2

2 3 V

4s23d3

2 4 Cr

4s13d5

2 5 Mn

4s23d5

2 6 Fe

4s23d6

2 7 Co

4s23d7

2 8 Ni

4s23d8

2 9 Cu

4s13d10

3 0 Zn

4s23d10

3 1 Ga

4s24p1

3 2 Ge

4s24p2

3 7 Rb

5s1

3 8 Sr

5s2

3 9 Y

5s24d12

4 0 Zr

5s24d2

4 1 Nb

5s24d3

4 2 Mo

5s14d5

4 3 Tc

5s23d5

4 4 Ru

5s14d7

4 5 Rh

5s14d8

4 6 Pd

4d10

4 7 Ag

5s14d10

4 8 Cd

5s24d10

4 9 In

5s25p1

5 0 Sn

5s25p2

5 1 Sb

5s25p3

5 5 Cs

6s1

5 6 Ba

6s2

5 7 L a *

6s25d1

7 2 Hf

6s25d2

7 3 Ta

6s25d3

74

W

6s25d4

7 5 Re

6s24d5

7 6 Os

6s25d6

7 7 Ir

5d76s2

7 8 Pt

6s15d9

7 9 Au

6s15d10

8 0 Hg

6s25d10

8 1 Tl

6s26p1

8 2 Pb

6s26p2

83

Bi

6s26p3

8 4 Po

6s26p4

8 7 Fr

7s1

8 8 Ra

7s2

8 9 Ac#

7s26d1

1 0 4 +

7s26d2

1 0 5 +

7s27d3

1 0 6 +

7s26d4

1 0 7 +

7s23d5

1 0 8 +

6s26d6

109 +

6d77s2

+ Element synthesized,

but no official name assigned

Family A Metals Q1. Maximum charge vs. family# ?Q2. Possible oxidation states of Sn?

Ions with multiple oxidation states

Reduction of Sn2+ ion:

Oxidation of Sn2+ ion: Sn2+ → Sn4+ + 2 e-

Q. Sn (Group IVA) has oxidation states of zero, plustwo, and plus four. Write half reactions depicting:

Sn2+ can act as an oxidizing or reducing agent inredox reactions!

Sn2+ + 2 e- → Sn

11A

18VIIIA

1H

1s12IIA

13IIIA

14IVA

15VA

16VIA

17VIIA

3Li

2s1

4Be

2s2 +2 !

+2 !

+2 !

+2 !

+2 !

1 1Na

3s1

1 2Mg

3s2

+3 3

IIIB

+ 4 4

IVB

+ 5 5

VB

+6 6

VIB

+7 7

VIIB

8VIIIB

+2 9 "

10 VIIIB

+1 11

IB

+2 12

IIB

1 3Al

3s23p1

1 9K

4s1

2 0Ca

4s2

2 1Sc

4s23d1

2 2Ti

4s23d2

2 3V

4s23d3

2 4Cr

4s13d5

2 5Mn

4s23d5

2 6Fe

4s23d6

2 7Co

4s23d7

2 8Ni

4s23d8

2 9Cu

4s13d10

3 0Zn

4s23d10

3 1Ga

4s24p1

3 2Ge

4s24p2

3 7Rb

5s1

3 8Sr

5s2

3 9Y

5s24d12

4 0Zr

5s24d2

4 1Nb

5s24d3

4 2Mo

5s14d5

4 3Tc

5s23d5

4 4Ru

5s14d7

4 5Rh

5s14d8

4 6Pd

4d10

4 7Ag

5s14d10

4 8Cd

5s24d10

4 9In

5s25p1

5 0Sn

5s25p2

5 1Sb

5s25p3

5 5Cs

6s1

5 6Ba

6s2

5 7

La*

6s25d1

7 2Hf

6s25d2

7 3Ta

6s25d3

7 4W

6s25d4

7 5Re

6s24d5

7 6Os

6s25d6

7 7Ir

5d76s2

7 8Pt

6s15d9

7 9Au

6s15d10

8 0Hg

6s25d10

8 1Tl

6s26p1

8 2Pb

6s26p2

8 3Bi

6s26p3

8 4Po

6s26p4

8 7Fr

7s1

8 8Ra

7s2

8 9Ac#

7s26d1

1 0 4 +

7s26d2

1 0 5 +

7s27d3

1 0 6 +

7s26d4

1 0 7 +

7s23d5

1 0 8 +

6s26d6

1 0 9 +

6d77s2

+ Element synthesized,

but no official name assigned

Transition Metals Q. Maximum oxidation state vs. family # ?

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Strength of Redox Agents

Example: 2 Na + Cl2 → 2 Νa+ + 2 Cl-

RA OA

RA: Na > Cl- OA: Cl2 > Na+

OA RA

The reactants are the stronger RAand OA and react spontaneously The non-reactive products are theweaker OA and RA.

_________________________________________

Redox agent strength

2 Sb + 3 Cl2 → 2 Sb3+ + 6 Cl-

OA RA

Q. Rank the strength of the reducing/oxidizing agentsin the reaction below:

RA strength:___ >___ OA strength: ___ >___

RA OA

Sb Cl - Cl2 Sb 3+

Reaction and Redox Strength

Cu(s) + Ag+(aq) → ? Ag(s) + Cu2+(aq) → ?

DEMO

If RA: Cu > Ag OA: Ag+ > Cu2+

Reactants

Reactions and Redox Strength

Cu(s) + Ag+(aq) → reaction

The weaker RA and OA do NOT react:

The stronger RA and OA react:

Ag(s) + Cu2+(aq) → no reaction

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Part I B. Predicting Metal Reactivity.

• Determine the reducing agent (RA) strength of fourteam assigned metals where the metal ions of allfour metals are available and only three of the fourmetals are available for experimental tests.

Experiment Design and Data Analysis

Example You need to determine the reducing agent strength of

Zn, Cu, and Mg.

ProblemAvailable: Solutions of Zn2+, Cu2+, and Mg2+. Zn and Cu only (i.e., Mg is unavailable)

Experiment Design for Part 1B.

•Mg•Cu•Zn

•Mg2+•Cu2+•Zn2+

Reducing agent species (metals) on one side andoxidizing agents species (metal ions) on other side.

Create a table for recording data (pre-lab).

Experiment Design and Data Analysis

Example:

Zn(s) + Cu2+ (aq) → reaction

Test available metal and metal ion combinations Record observations

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Check data. Does it make sense?

11# rxns.

1RxnCu

1RxnZn

# rxns.Cu2+Zn2+

“ These results don’t make sense!”

Only one combination of metal and metal ion should react spontaneously -- the stronger RA and OA!

•1•0•# rxns.

•0No•No•Cu

•1•ReactionNo•Zn

•# rxns.•Cu2+•Zn2+

Data Analysis

RA and OA strength are inverse:

RA: Zn > Cu OA: Cu2+ > Zn2+

This data makes sense: The stronger RA and OA show more reactions!

No•Mg•NoNo•No•Cu•No•Rxn.No•Zn

•Mg2+•Cu2+•Zn2+

Reducing Agent Strength of Mg, Zn, and Cu?

Mg > Zn > Cu

Q2. Comparative RA strength of the metals?

Q1. Complete the table below.

Rxn Rxn

RA strength: _______________

Part I A. Metal reactions with water.

• Rank the reducing agent strength of the metals Na,K, Mg, and Ca from experimental observations.

• Correlate the results with the position of the metalin the periodic table.

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Experimental Comparison of Ca and Mg

Metal + Water → metal hydroxide + H2(g) RA OA OA RAExample: Mg(s) + 2HOH(l) → Mg(OH)2(s) + H2(g)

Ca > Mg

DEMO

RA: ________________

Reactivity of K and Na

Experimental determination of the reactivity of K andNa compared to Ca and Mg.

DEMO

Experimental Comparison of K, Na, Ca, and Mg

RA: K > Na > Ca > Mg

Na skitters around the K skitters around the water surface water surface and ignites

Electronegativity of the elements1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17IA IIA IIIB IVB VB VIB VIIB VIIIB IB IIB IIIA IVA VA VIA VIIA

H2.1Li1.0

Be1.5

B2.0

C2.5

N3.0

O3.5

F4.0

Na0.9

Mg1.2

Al

1.5

Si1.8

P2.1

S2.5

Cl3.0

K0.8

Ca1.0

Sc1.3

Ti1.5

V1.6

Cr1.6

Mn1.5

Fe1.8

Co1.8

Ni1.8

Cu1.9

Zn1.6

Ga1.6

Ge1.8

As2.0

Se2.4

Br2.8

Rb0.8

Sr1.0

Y1.2

Zr1.4

Nb1.6

Mo1.8

Tc1.9

Ru2.2

Rh2.2

Pd2.2

Ag1.9

Cd1.7

In1.7

Sn1.8

Sb1.9

Te2.1

I2.5

Cs0.7

Ba0.9

La-Lu

Hf1.3

Ta1.5

W1.7

Re1.9

Os2.2

Ir2.2

Pt2.2

Au2.4

Hg1.9

Tl1.8

Pb1.8

Bi1.9

Po2.0

At2.2

Fr0.7

Ra0.9

Ac1.1

Th1.3

Pa1.5

U1.7

Np- No1.3

= Metalloids = Nonmetals = Metals

RA and OA Predictions from Electronegativity values = Electron pulling power of an atom when part of a bond

8

IA IIA IIIB IVB VB VIB VIIB VIIIB IB IIB IIIA IVA VA VIA VIIA

H2.1Li1.0

Be1.5

B2.0

C2.5

N3.0

O

3.5F4.0

Na0.9

Mg1.2

Al

1.5

Si1.8

P2.1

S2.5

Cl3.0

K0.8

Ca1.0

Sc1.3

Ti1.5

V1.6

Cr1.6

Mn1.5

Fe1.8

Co1.8

Ni1.8

Cu1.9

Zn1.6

Ga1.6

Ge1.8

As2.0

Se2.4

Br2.8

Rb0.8

Sr1.0

Y1.2

Zr1.4

Nb1.6

Mo1.8

Tc1.9

Ru2.2

Rh2.2

Pd2.2

Ag1.9

Cd1.7

In1.7

Sn1.8

Sb1.9

Te2.1

I2.5

Cs0.7

Ba0.9

La-Lu

Hf1.3

Ta1.5

W1.7

Re1.9

Os2.2

Ir2.2

Pt2.2

Au2.4

Hg1.9

Tl1.8

Pb1.8

Bi1.9

Po2.0

At2.2

Fr0.7

Ra

0.9Ac1.1

Th1.3

Pa1.5

U1.7

Np- No1.3

Q. Predict the RA strength of K compared to Na, Mg,and Ca based on position and electronegativity values.

K > Na > Ca > Mg____> _____ > _____ > _____

IA IIA IIIB IVB VB VIB VIIB VIIIB IB IIB IIIA IVA VA VIA VIIA

H2.1Li1.0

Be1.5

B2.0

C2.5

N3.0

O3.5

F4.0

Na0.9

Mg1.2

Al

1.5

Si1.8

P2.1

S2.5

Cl3.0

K0.8

Ca1.0

Sc1.3

Ti1.5

V1.6

Cr1.6

Mn1.5

Fe1.8

Co1.8

Ni1.8

Cu1.9

Zn1.6

Ga1.6

Ge1.8

As2.0

Se2.4

Br2.8

Rb0.8

Sr1.0

Y1.2

Zr1.4

Nb1.6

Mo1.8

Tc1.9

Ru2.2

Rh2.2

Pd2.2

Ag1.9

Cd1.7

In1.7

Sn1.8

Sb1.9

Te2.1

I2.5

Cs0.7

Ba0.9

La-Lu

Hf1.3

Ta1.5

W1.7

Re1.9

Os2.2

Ir2.2

Pt2.2

Au2.4

Hg1.9

Tl1.8

Pb1.8

Bi1.9

Po2.0

At2.2

Fr0.7

Ra

0.9Ac1.1

Th1.3

Pa1.5

U1.7

Np- No1.3

Q. Where are the best reducing and oxidizing agents located?

Caution: Attraction of metal or nonmetal ion for electrons in abond is different from its metal or nonmetal element.

Questions?Contact nkerner@umich.edu