Question

1. Choose one of the transition or inner transition metals from the periodic table. Nickel Using your book (Chapter 23 may be very useful) and Internet resources, discuss why your transition metal and their compounds display a variety of color. Be sure to include in your discussion, important oxidation states, the electron configuration and how the d-electrons are involved. How can you include the electromagnetic spectrum and the nature of light into your discussion? How is energy and wavelength related? Use your knowledge of the emission and absorption of light in your discussion. Remember to site your sources in APA style. Respond to at least two other students. Contribute to an ongoing discussion by responding to comments made to your posting or to comments made by other students to other postings. 1. Choose one of the transition or inner transition metals from the periodic table. Nickel 2. Using your book (Chapter 23 may be very useful) and Internet resources, discuss why your transition metal and their compounds display a variety of color. Be sure to include in your discussion, important oxidation states, the electron configuration and how the d-electrons are involved. 3. How can you include the electromagnetic spectrum and the nature of light into your discussion? How is energy and wavelength related? Use your knowledge of the emission and absorption of light in your discussion. 4. Remember to site your sources in APA style.

Answer 1

And we know that transition elements show variable oxidation states so the electrons will be filled differently in each case and hence during excitation and relaxing process the number of electrons varies which will excite and relax which is known as d-d transition.

For an octahedral geometry: When an electron excite from t_2g level to e_g and eg electrons relax and again come to t2g this process is known as d-d transition and it is the responsible for the color of so many transition elements.

There are other factors which are also responsible for the color of a compound and that is charge transfer, which is of two types LMCT (Ligand to Metal Charge transfer) and MLCT (Metal to Ligand Charge Transfer). Compounds like CuSO4.5H2O is colored because of charge transfer (LMCT).

The strength of ligand also affect the color of the complex since strong field ligand can start pairing in orbital and forms an inner orbital complex and show color but weak field ligands don't involve any pairing and form an outer orbital complex and don't show the color of the compound.