1. Choose one of the transition or inner transition metals from the periodic tab

Question

1.      Choose one of the transition or inner transition metals from the periodic table. I choose the element cobalt. cobalamin (vitamin B12)

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

Explanation / Answer

2. The light which passes through the transition metal compounds will have all the colours in it except for the color that is absorbed. We see the complementary color of the color that was absorbed.

Common oxidation states of cobalt include +2 and +3. A common oxidation state for simple compounds is +2 (cobalt(II)). These salts form the pink-colored metal aquo complex[Co(H2O)6]2+ in water. Addition of chloride gives the intensely blue [CoCl4].

Electronic configuration of cobalt: [Ar] 3d7 4s2

d-electrons are able to absorb certain frequencies of electromagnetic radiation to get promoted to higher energy orbitals and form stable compounds. These frequencies have a certain energy which correspond to the energy difference between different orbitals (dxy, dyz, dxz, dx2-y2, dz2).

3.

Transition metal and their compounds have an energy difference between the non-degenerate d orbitals which correspond to the energy of radiation within the visible light spectrum. This means that when we look at the metal complex, we don't see the entire visible light spectrum, but only a part of it.

Energy corresponding to the walvelength of the light absorbed: Energy = hc /

4.

Sources:

1. https://en.wikipedia.org/wiki/Cobalt

2. http://chemistry.stackexchange.com/questions/4667/why-do-transition-elements-make-colored-compounds

3. https://www.wou.edu/las/physci/ch462/tmcolors.htm

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