MCAT Question A Day - 10/29/14 - Answer!
Aluminum has only one oxidation state, while chromium has several. Which of the following is the best explanation for this difference?
A. Electrons in the d orbitals of Cr mayor may not be used to form bonds.
B. Electrons in the p orbitals of Cr mayor may not be used to form bonds.
C. Electrons in the d orbitals of Al may or may not be used to form bonds.
D. Electrons in the p orbitals of AI may or may not be used to form bonds.
A is correct. Since chromium forms more than one oxidation state and aluminum forms only one, chromium requires the variability in number of bonds formed. This means choices C and D are out. Chromium has electrons in the orbitals of the 2p subshell, but these are core electrons and not used for making bonds. Chromium has 6 valence electrons, 5 of which are in the orbitals of the 3d subshell.
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