Colors of actinides and transitions in actinide series

This presentation basically covers the colors and transition in Actinide series

1. COLOUR OF ACTINIDES The Colour of Actinides depends on the number of unpaired electrons. When 5f orbital is empty , half-filled or full, such ions are found to be colourless. Ac3+ ion (f0) Cm3+ (f7) Lw3+ (f14) Most of the tripositive and tetra positive actinides ions are coloured.

2. Coloured compounds arises due to f-f electronic transition. Colours are produced (in aqueous solution of actinide salts) when an electron jumps from one energy level to the other within 5f-orbitals . f-f ELECTRONIC TRANSITION Fig: f-f Transition

3. COLOUR OF ACTINIDES Elements Colour Actinium Colourless Thorium Colourless Protactinium Colourless Uranium Green Fig: Uranium +4 state

4. Elements Colour Neptunium Blue or purple Plutonium Blue or violet Americium Pink Curium Colourless COLOUR OF ACTINIDES Fig: Colour of Neptunium

5. More complicated Spectra . Reasons: The 5f electrons have greater penetrating effect and come closer to the nucleus . Influence of ligand field effect. Narrow bands (compared to transition metal spectra).
Intensities are 10 times larger those of lanthanide bands. SPECTRA OF ACTINIDES Fig: Spectra of Actinides

6. The bands of actinide ions arise from electronic transition . When the light, interacts with actinide atoms, elections can absorb energy . Absorption of light causes the electrons to move from lower to higher energy levels leading to formation of absorption bands in spectra. ABSORPTION BANDS Fig: Absorption of energy

7. ELECTRONIC SPECTRA OF ACTINIDES Electronic spectra of actinides arises due to following transitions. f-f transitions f-d transitions Metal to ligand charge transfer Fig: Electronic spectra of Actinides

8. ELECTRONIC SPECTRA OF ACTINIDES f-f Transitions Laporte Forbidden Transition The Narrow and sharp bands Bands in visible and U.V region f-d Transitions Laporte and spin allowed transitions Intense and broad bands Bands are confined to U. V region Metal to ligand charge transfer Allowed transition. Intense and broad absorption Found in U. V region