Transition Metals Quantum Numbers Electron Configuration of Transition

Metals SPDF Electron Spin

Examples Colors of Transition Metals Compound Conclusion

These elements are : Very hard High melting points High boiling points High electrical conductivity Malleable Have Color in compound

Electrons are arranged according to energy levels in an atom

Each sublevel is broken into orbitals sharp, principal, diffuse, and

fundamentalEach orbital can hold a maximum of

2 electrons

Sublevel Max no. of electrons # orbitals

s 2 1

p 6 3

d 10 5

f 14 7

Energy level

Atom: CarbonAtomic no. : 6

Electron Have spin which gives to tiny magnetic field and to a spin quantum number (ml)

Hund’s Rule: if 2 or more orbitals with the same energy are available, one electron goes into each until all are half-full. The electrons in the half-filled orbitals all have the same spin.

Aufbau Principle: Lower-energy orbitals fill before higher-energy orbitals.

ArgonElectronic config: 18

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ScandiumElectronic config: 21

Order of filling of electron states

The colour type and intensity is due to an interplay of the photons reflecting upon the electronic orbitals and ligands

Copyright © 2008 by Republic Polytechnic, Singapore

Transition metals are found in the d-block in the periodic table, between the s- and p-blocks

The order of filling of electron states explains the behaviour of the d-block elements in an spdf fashion.

ie: electron filling based on energy levels

They take on a different set of chemical properties

Robby thinks he don’t need to add his slide’s points in this portion, he’ll explain everything again! :D

Colours of compounds are determined by the level of electromagnetic energy(i.e. light) absorbed by the electrons of the compound.

The level of energies absorbed by the compound depends on the energy levels in the electron clouds of the compound.

Energy needed for an electron to make the transition between d orbitals is less when the number of paired electrons within the 5 orbitals is the same before and after the transition. This is called a "Spin Allowed" Transition.

e.g., For Fe2+ there are 6 d electrons spread among 5 d orbitals

=> 4 of the orbitals have unpaired electrons and the fifth has a pair of electrons. Absorption of a photon would simply cause the second electron in the pair to pair up with one of the unpaired electrons. The result would still be 4 unpaired and 1 paired.

i.e., before transition: 4 UNPAIRED, 1 PAIRED after transition: 4 UNPAIRED, 1 PAIRED-This would result in the absorption of lower energy wavelengths

e.g., yellows and reds => minerals would show blue - green colors

Energy needed for an electron to make the transition between d orbitals is more when the number of paired electrons within the 5 orbitals is different after the transition. This is called a "Spin Forbidden" Transition.

e.g., For Fe3+ there are 5 d electrons spread among 5 d orbitals

=> initially all 5 of the orbitals have unpaired electrons, and there would be no pairs. Absorption of a photon would cause one of these unpaired electrons to jump up and pair with one of the other unpaired electrons. The result would be 3 unpaired and 1 paired.

i.e., before transition: 5 UNPAIRED, 0 PAIRED after transition: 3 UNPAIRED, 1 PAIRED-This would result in the absorption of higher energy wavelengths

e.g., greens and blues => minerals would show yellow - red colors

• Coordination numbersHigher coordination numbers (no. of ligands) results in longer

distances between the central ion (Fe2+) and the coordinating ion (O-). This greater distance results in lower energy levels for the cation's electrons => absorb lower energy wavelengths compared to the same cation with fewer (closer) coordinating ions.

e.g., Fe2+ in 6CN absorbs higher energy wavelengths than Fe2+ in 8CN

• Bond strengthStrong bonds result in higher energy electron states => absorb

higher energy photons e.g., Ionic bonds in corundum result in absorption of blues and greens in ruby (gem form of corundum)

Weaker bonds result in lower energy electron states => absorb lower energy photons e.g., Covalent bonds in beryl result in absorption of reds and yellow in emerald (gem form of beryl)