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Prepared by Lawrence Kok

Tutorial on Absorption spectrum and Line Emission/Absorption Spectrum.

Why transition metals ion complexes have diff colour?

Transition Metal – Colour Complexes

Colour you see is BLUE – Blue reflected/transmitted to your eyes - Red/orange absorbed (complementary colour)

Colour you see is Yellow – Yellow reflected/transmitted to your eyes - Violet absorbed (complementary colour)

complementary colour

Bluetransmitted

Wave length - absorbed

Wave length - absorbed

Visible light

Visible light

Yellowtransmitted

absorbed

Formation coloured complexes Variable Colours

Click here vanadium ion complexes Click here nickel ion complexes

V5+/ VO2+ -

yellowV4+/ VO2+ - blueV3+ - greenV2+ - violet

NiCI2 - YellowNiSO4 - GreenNi(NO3)2

- VioletNiS - Black

Diff oxidation states

Colour formation

Nature of transition metal

Oxidation state

Diff ligands ShapeStereochemistry

Diff ligandsDiff metals

MnCI2 - PinkMnSO4 - RedMnO2 - BlackMnO4

- - Purple

Cr2O3 - GreenCrO4

2- -

YellowCrO3 - RedCr2O7

2- -

Orange

Shape/ Stereochemistry

Tetrahedral Octahedral

BlueYellow

Transition Metal – Colour Complexes

Ion Electron configurati

on

Colour

Sc3+ [Ar] colourless

Ti3+ [Ar]3d1 Violet

V3+ [Ar]3d2 Green

Cr3+ [Ar]3d3 Violet

Mn2+ [Ar]3d5 Pink

Fe2+ [Ar]3d6 Green

Co2+ [Ar]3d7 Pink

Ni2+ [Ar]3d8 Green

Cu2+ [Ar]3d9 Blue

Zn2+ [Ar]3d10 colourless

Ion configuration

Colour

Ti3+ [Ar] 3d1 Violet

V3+ [Ar] 3d2 Green

Cr3+ [Ar] 3d3 Violet

Mn2

+

[Ar] 3d5 Pink

Fe2+ [Ar] 3d6 Green

Co2+ [Ar] 3d7 Pink

NO ligand• Degenerate• 3d orbital same energy level • five 3d orbital equal in energy

Five 3d orbital (Degenerate – same energy level)

Transition Metal – Colour Complexes

Presence of ligand • 3d orbital split• five 3d orbital unequal in energy

Mn2+ [Ar]3d5

3d yz3d xy 3d xz 3d Z23dx

2 - y2

∆E

lies between axes lies along axes

Mn2+

:L:L:L

Colour- Splitting 3d orbital by ligand

:L:L:L

:L

:L

:L

:L

:L:L

3d xy 3d xz 3d yz 3dx2 - y

2 3d Z2

No ligand – No repulsion – No splitting 3d orbitals

Mn2+

No ligands approaching

:L

:L

:L

:L

:L:L

:L

:L :L

:L :L

:L

:L

:L:L

:L :L

:L

:L

:L

:L

:L

:L

:L

Ligands approaching

Ligand approach not directly with 3d electron Less repulsion bet 3d with ligand Lower in energy

Ligand approach directly 3d electron More repulsion bet 3d with ligand Higher in energy

With ligand• Splitting of 3d orbital• 3d orbital unequal

energy

Elec/elec repulsion bet 3d e with ligand

Colour- Splitting of 3d orbital of metal ion by ligand

NO ligand• Degenerate• 3d orbital same energy level • five 3d orbital equal in energy

Five 3d orbital (Degenerate – same energy level)

Splitting 3d orbital Electronic transition possiblePhoton light absorb to excite elec

With ligand• Splitting of 3d orbital• 3d orbitals unequal energy

Why Ti 3+ ion solution is violet ?

violet

Transition Metal – Colour Complexes

Presence of ligand • 3d orbital split• five 3d orbital unequal in energy

Ti3+ [Ar] 3d1

3d yz3d xy 3d xz 3d Z23d x

2 - y2

Ti3+ [Ar] 3d1 ∆E

Ion configuration

Colour

Sc3+ [Ar] colourless

Ti3+ [Ar] 3d1 Violet

V3+ [Ar] 3d2 Green

Cr3+ [Ar] 3d3 Violet

Mn2

+

[Ar] 3d5 Pink

Fe2+ [Ar] 3d6 Green

Co2+ [Ar] 3d7 Pink

Ni2+ [Ar] 3d8 Green

Cu2+ [Ar] 3d9 Blue

Zn2+ [Ar] 3d10 colourless

Green / yellow wavelength - Abosrb to excite electron

О

Colour- Splitting of 3d orbital of metal ion by ligand

NO ligand• Degenerate• 3d orbital same energy level • five 3d orbital equal in energy

Five 3d orbital (Degenerate – same energy level)

Splitting 3d orbital Electronic transition possiblePhoton light absorb to excite elec

With ligand• Splitting of 3d orbital• 3d orbitals unequal energy

Why Cu3+ ion solution is blue ?

Blue

Transition Metal – Colour Complexes

Presence of ligand • 3d orbital split• five 3d orbital unequal in energy

Cu2+ [Ar] 3d9

3d yz3d xy 3d xz 3d Z23d x

2 - y2

Cu2+ [Ar] 3d9 ∆E

Ion configuration

Colour

Sc3+ [Ar] colourless

Ti3+ [Ar] 3d1 Violet

V3+ [Ar] 3d2 Green

Cr3+ [Ar] 3d3 Violet

Mn2

+

[Ar] 3d5 Pink

Fe2+ [Ar] 3d6 Green

Co2+ [Ar] 3d7 Pink

Ni2+ [Ar] 3d8 Green

Cu2+ [Ar] 3d9 Blue

Zn2+ [Ar] 3d10 colourless

Red / orange wavelength - Abosrb to excite electron

О

Cu2+

Colour- Splitting of 3d orbital of metal ion by ligand

NO ligand• Degenerate• 3d orbital same energy level • five 3d orbital equal in energy

Five 3d orbital (Degenerate – same energy level)

Splitting 3d orbitalNO electronNO absorption lightNO electronic transition possible

With ligand• Splitting of 3d orbital• 3d orbital unequal energy

Why Sc 3+ ion solution is colourless ?

Colourless

Transition Metal – Colour Complexes

Presence of ligand • 3d orbital split• five 3d orbital unequal in energy

Sc3+ [Ar] 3d0

3d yz3d xy 3d xz 3d Z23d x

2 - y2

Sc3+ [Ar] 3d0 ∆E

Ion configuration

Colour

Sc3+ [Ar] colourless

Ti3+ [Ar] 3d1 Violet

V3+ [Ar] 3d2 Green

Cr3+ [Ar] 3d3 Violet

Mn2

+

[Ar] 3d5 Pink

Fe2+ [Ar] 3d6 Green

Co2+ [Ar] 3d7 Pink

Ni2+ [Ar] 3d8 Green

Cu2+ [Ar] 3d9 Blue

Zn2+ [Ar] 3d10 colourless

All wavelength transmitted

Sc3+

NO absorption

white

Colour- Splitting of 3d orbital of metal ion by ligand

NO ligand• Degenerate• 3d orbital same energy level • five 3d orbital equal in energy

Five 3d orbital (Degenerate – same energy level)

With ligand• Splitting of 3d orbital• 3d orbital unequal energy

Why Zn 3+ ion solution is colourless ?

Colourless

Transition Metal – Colour Complexes

Presence of ligand • 3d orbital split• five 3d orbital unequal in energy

Zn2+ [Ar] 3d10

3d yz3d xy 3d xz 3d Z23d x

2 - y2

Zn2+ [Ar] 3d10 ∆E

Ion configuration

Colour

Sc3+ [Ar] colourless

Ti3+ [Ar] 3d1 Violet

V3+ [Ar] 3d2 Green

Cr3+ [Ar] 3d3 Violet

Mn2

+

[Ar] 3d5 Pink

Fe2+ [Ar] 3d6 Green

Co2+ [Ar] 3d7 Pink

Ni2+ [Ar] 3d8 Green

Cu2+ [Ar] 3d9 Blue

Zn2+ [Ar] 3d10 colourless

Zn2+

All wavelength transmitted Splitting 3d orbitalFULLY FILLEDNO absorption lightNO electronic transition possible

NO absorption

white

Colour- Splitting of 3d orbital of metal ion by ligand

NO ligand• Degenerate• 3d orbital same energy level • five 3d orbital equal in energy

Five 3d orbital (Degenerate – same energy level)

With ligand• Splitting of 3d orbital• 3d orbital unequal energy

Why Cu+ ion solution is colourless ?

Colourless

Transition Metal – Colour Complexes

Presence of ligand • 3d orbital split• five 3d orbital unequal in energy

Cu+ [Ar] 3d10

3d yz3d xy 3d xz 3d Z23d x

2 - y2

Cu+ [Ar] 3d10 ∆E

Cu+

All wavelength transmitted Splitting 3d orbitalFULLY FILLEDNO absorption lightNO electronic transition possible

Ion configuration

Colour

Sc3+ [Ar] colourless

Ti3+ [Ar] 3d1 Violet

V3+ [Ar] 3d2 Green

Cr3+ [Ar] 3d3 Violet

Mn2

+

[Ar] 3d5 Pink

Cu+ [Ar] 3d10 Colourless

Cu2+ [Ar] 3d9 Blue

white

NO absorption

Colour- Splitting of 3d orbital of metal ion by ligand

NO ligand• Degenerate• 3d orbital same energy level • five 3d orbital equal in energy

Five 3d orbital (Degenerate – same energy level)

No ligand/Water• NO Splitting 3d orbital• 3d orbital equal energy

Why Cu3+ ion anhydrous is colourless ?

Transition Metal – Colour Complexes

NO ligand • 3d orbital split• five 3d orbital equal in energy

Cu2+ [Ar] 3d9

3d yz3d xy 3d xz 3d Z23d x

2 - y2

Cu2+ [Ar] 3d9

Ion configuration

Colour

Sc3+ [Ar] colourless

Ti3+ [Ar] 3d1 Violet

V3+ [Ar] 3d2 Green

Cr3+ [Ar] 3d3 Violet

Mn2

+

[Ar] 3d5 Pink

Fe2+ [Ar] 3d6 Green

Co2+ [Ar] 3d7 Pink

Ni2+ [Ar] 3d8 Green

Cu2+ [Ar] 3d9 Blue

Cu2+

Colourless

NO Splitting 3d orbitalNO absorption lightNO electronic transition possible

All wavelength transmit

white

NO absorption

Formation coloured complexes

V5+/ VO2+ -

yellowV4+/ VO2+ - blueV3+ - greenV2+ - violet

NiCI2 - YellowNiSO4 - GreenNi(NO3)2

- VioletNiS - Black

Diff oxidation states

Colour formation

Nature of transition metal

Diff ligands

Diff metals

MnCI2 - PinkMnSO4 - RedMnO2 - BlackMnO4

- - Purple

Cr2O3 - GreenCrO4

2- -

YellowCrO3 - RedCr2O7

2- -

Orange

Shape/ Stereochemistry

Tetrahedral Octahedral

BlueYellow

Transition Metal – Colour Complexes

Ion configuration

Colour

Ti3+ [Ar]3d1 Violet

V3+ [Ar]3d2 Green

Cr3+ [Ar]3d3 Violet

Mn2+ [Ar]3d5 Pink

Fe2+ [Ar]3d6 Green

Co2+ [Ar]3d7 Pink

Ni2+ [Ar]3d8 Green

Cu2+ [Ar]3d9 Blue

Colour- Splitting 3d orbital by ligand

Strong ligand (higher charge density)↓

Greater splitting↓

Diff colour

Weak ligand (Low charge density)↓

Smaller splitting↓

Diff colour

No ligand↓

No splitting↓

No colour

Spectrochemical series – Strong ligand → Weak Ligand

Co/CN > en > NH3 > SCN- > H2O > C2O42- > OH- > F- > CI- > Br- > I-

NO ligand – NO splitting 3d orbital (Same energy level)

WEAK ligand – small splitting 3d orbital (Unequal energy)

∆E∆E

STRONG ligand – greater splitting 3d orbital (Unequal energy)

I- < Br- < CI- < F- < OH- < C2O42- < H2O < SCN- < NH3 < en < Co/CN

Transition Metal – Colour Complexes

Colour- Splitting 3d orbital by ligand

Strong ligand (higher charge density)↓

Greater splitting - ↑∆E Diff colour

Weak ligand (Low charge density)↓

Smaller splitting - ↓∆ EDiff colour

No ligand↓

No splittingNo colour

Spectrochemical series – Weak ligand → Strong Ligand

NO ligand – NO splitting 3d orbital (Same energy level)

WEAK ligand – small splitting 3d orbital (Unequal energy)

∆E ∆E

STRONG ligand – greater splitting 3d orbital (Unequal energy)

Very Strong ligand ↓

Greater splitting - ↑∆EDiff colour

∆E

Ion ES Colour

Cu(CI4)2- 3d9 Colourless

Cu(CI4)2- 3d9 Green

Cu(H2O)62+ 3d9 Blue

Cu(NH3)42

+

3d9 Violet

Cu2+ [Ar] 3d9 STRONGEST ligand – greatest splitting

ООО

Ligand I- Br- CI- F- C2O42

-

H2O SCN-

NH3 en Co/CN-

ʎ (wavelength)

longest shortest

∆E Weak field

SmallestSplit

Strong field

HighestSplit

[Cu(CI)4]2- [Cu(NH3)4]2+[Cu(H2O)6]2+

О О О

H2O stronger ligand↓

Greater spitting ∆E↓

Higher energy wavelength absorbed

CI- weak ligand↓

Small spitting ∆E↓

Low energy wavelength absorbed

NH3 strongest ligand↓

Greatest spitting ∆E↓

Highest energy wavelength absorbed

- Higher energy absorbed- Orange wavelength absorb to excite electron

- Highest energy absorbed- Yellow wavelength absorb to excite electron

Transition Metal – Colour Complexes

Colour- Splitting 3d orbital by ligand

Strong ligand (higher charge density)↓

Greater splitting - ↑∆E - Diff colour

Weak ligand (Low charge density)↓

Smaller splitting - ↓∆ E - Diff colour

Spectrochemical series – Weak ligand → Strong Ligand

WEAK ligand – small splitting 3d orbital (Unequal energy)

∆E∆E

STRONG ligand – greater splitting 3d orbital (Unequal energy)

Very Strong ligand ↓

Greater splitting - ↑∆E- Diff colour

∆E

Cu(H2O)62+ 3d9 Blue

STRONGEST ligand – greatest splitting

[Cu(NH3)4]2+[Cu(H2O)6]2+

- Lower energy absorbed - Red wavelength absorb to excite electron

[Cu(CI)4]2-

Cu(CI4)2- 3d9 Green Cu(NH3)42

+

3d9 Violet

Nuclear charge - +5↓

Strong ESF atrraction bet –ve ligand↓

Greatest splitting ∆E↓

Highest energy wavelength absorb

Nuclear charge - +3↓

Strong ESF atrraction bet –ve ligand↓

Greater splitting ∆E↓

Higher energy wavelength absorb

Mn(H2O)62

+

+2 PINK

Nuclear charge - +2↓

Weak ESF atrraction bet –ve ligand↓

Smaller splitting ∆E↓

Low energy wavelength absorb

- Higher energy absorbed- Blue wavelength absorb to excite electron

- Highest energy absorbed- Violet wavelength absorb to excite electron

Transition Metal – Colour Complexes

Colour- Splitting 3d orbital by ligand

High nuclear charge / charge density↓

Greater splitting - ↑∆E - Diff colour

Low nuclear charge /charge density↓

Smaller splitting - ↓∆ E - Diff colour

Nuclear charge on metal ion

Low nuclear charge – small splitting 3d orbital (Unequal energy)

∆E∆E

High nuclear charge – greater splitting 3d orbital (Unequal energy)

Highest nuclear charge/charge density↓

Greatest splitting - ↑∆E- Diff colour

∆E

Fe(H2O)63+ +3 YELLOW

HIGHEST nuclear charge – greatest splitting

Fe(H2O)63+

- Lower energy absorbed - Green wavelength absorb to excite electron

V(H2O)65+ +5 YELLOW/GREEN

Mn(H2O)62+ V(H2O)6

5+

Oxidation number - +3↓

Strong ESF atrraction bet –ve ligand↓

Greater splitting ∆E↓

Higher energy wavelength absorb

Oxidation number - +2↓

Weak ESF atrraction bet –ve ligand↓

Smaller splitting ∆E↓

Low energy wavelength absorb

Transition Metal – Colour Complexes

Colour- Splitting 3d orbital by ligand

Higher oxidation number/charge density↓

Greater splitting - ↑∆E - Diff colour

Lower ESF attraction – small splitting 3d orbital (Unequal energy)

∆E∆E

STRONG ligand – greater splitting 3d orbital (Unequal energy)

∆E

Fe(H2O)63+ +3 Yellow

- Lower energy absorbed - Red wavelength absorb to excite electron

Fe(H2O)62+ +2 Green

Oxidation number on metal ion

Low oxidation number /charge density↓

Smaller splitting - ↓∆ E - Diff colour

Fe(H2O)62+

- Higher energy absorbed- Blue wavelength absorb to excite electron

Fe(H2O)63+

V(H2O)65+ +5 YELLOW/GREEN

Highest oxidation number/charge density↓

Greatest splitting - ↑∆E- Diff colour

HIGHEST nuclear charge – greatest splitting

- Highest energy absorbed- Violet wavelength absorbed to excite electron

Nuclear charge - +5↓

Strongest ESF atrraction bet –ve ligand↓

Greatest splitting ∆E↓

Highest energy wavelength absorb

V(H2O)65+

Electromagnetic Spectrum

Electromagnetic spectrum ranges from Radiowaves to Gamma waves.- Form of energy- Shorter wavelength -> Higher frequency -> Higher energy- Longer wavelength -> Lower frequency -> Lower energy

Electromagnetic radiation • Travel at speed of light, c = fλ -> 3.0 x 108 m/s• Light Particle – photon have energy given by -> E = hf• Energy photon - proportional to frequency

Inverse relationship between- λ and fWavelength, λ - long

Frequency, f - low

Wavelength, λ - short

Frequency, f - high

Plank constant • proportionality constant bet energy and freq

Excellent video wave propagation Click here to view.

Electromagnetic Wave propagation.

Wave

Electromagnetic radiation

Electromagnetic radiation • Moving charges/particles through space • Oscillating wave like property of electric and magnetic field• Electric and magnetic field oscillate perpendicular to each other and perpendicular to direction of wave propagation.

Electromagnetic wave propagation

wave

Wave – wavelength and frequency - travel at speed of light

Violet

λ = 410nm

Red

f = c/λ = 3 x 108/410 x 10-9

= 7.31 x 1014 Hz

E = hf = 6.626 x 10-34 x 7.31 x 1014

= 4.84 x 10-19 J

λ = 700nm

f = c/λ = 3 x 108/700 x 10-9

= 4.28 x 1014 Hz

E = hf = 6.626 x 10-34 x 4.28 x 1014

= 2.83 x 10-19 J

Click here to view video

Light given off

Continuous Spectrum :Light spectrum with all wavelength/frequency

Emission Line Spectrum :• Spectrum with discrete wavelength/ frequency • Emitted when excited electrons drop from higher to

lower energy level

Absorption Line Spectrum :• Spectrum with discrete wavelength/frequency • Absorbed when ground state electrons are excited

Atomic Emission Vs Atomic Absorption Spectroscopy

Ground state

Excited stateElectrons from excited state

Emit radiation when drop to ground state

Radiation emitted

Emission Spectrum

Electrons from ground state

Absorb radiationto excited state

Electrons in excited state

Radiation absorbed

Continuous Spectrum Vs Line Spectrum

Light/photon ABSORB by electron

Range Light/photon ABSORB by electron

Light/photon ABSORB by electron

Absorption spectrum is broad/continuousIons in solution (Solvent)

2

∞ Absorption spectrum for ions in solution↓

Surrounded by ligand and solvent↓

Have electronic excitation transition state + vibrational/rotational energy level

↓Continuous broad spectrum

Gaseous state – only gaseous ion present↓

Complete vacuum↓

Well defined spectral line exist↓

Either excited or not↓

Only electronic transition state allowed

1

2

3

45

Light given off

Absorption/Emission spectrum -discrete/fixed/lineGaseous ions (Vacuum) Vs

Electronic ground state

Electronic excited state

Line emission spectrum Line absorption spectrum

Electronic ground state

1

Electronic excited state

3

Vibrational energy level

Rotational energy level

Whole range of wavelength/broad spectrum can be absorbed to excite electron to electronic/vibrational/ rotational level

Absorption spectrum is broad/continuousIons in solution (Solvent)

2

No line emission spectrum seen as electron drop to lower level

↓Energy is lost in small steps to solvent/environment

Electronic ground state

1

Electronic excited state

3

Vibrational energy level

Rotational energy level

Whole range of wavelength/broad spectrum can be absorbed to excite electron to electronic/vibrational/rotational level

Absorption spectrum for ions in solution↓

Surrounded by ligand and solvent↓

Have electronic excitation transition state + vibrational/rotational energy level

↓Continuous broad spectrum

Absorption spectrum is broad/continuousIons in solution (Solvent)

Whole range of wavelength/broad spectrum can be absorbed to excite electron to electronic/vibrational/rotational level

Electronic ground state1

2

3

Range Light/photon ABSORB by electron

Electronic excited stateVibrational energy level

Rotational energy level

Energy lost in small stepsAbsorbed by solventLost to environment

Acknowledgements

Thanks to source of pictures and video used in this presentation

http://crescentok.com/staff/jaskew/isr/tigerchem/econfig/electron4.htmhttp://pureinfotech.com/wp-content/uploads/2012/09/periodicTable_20120926101018.png

Thanks to Creative Commons for excellent contribution on licenseshttp://creativecommons.org/licenses/

Prepared by Lawrence Kok

Check out more video tutorials from my site and hope you enjoy this tutorialhttp://lawrencekok.blogspot.com