The question asks which M3+ ions (where M is a metal) are predicted to have the following ground-state electron configurations:
a.) [Ar]3d6
b.) [Ar]3d5
The solutions manual says a is Co3+ and b is Fe3+ but could someone explain how they got this answer?
Thanks!
Question 3.11
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DomMaiorca_1I
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Re: Question 3.11
It's pretty much just calculating the ground state in reverse. Knowing that the noble gas is Argon, the metal(s) must come from the fourth period of the periodic table since Argon is located in the third.
a) 3d6 tells you there is 6 electrons, but you need to add an additional 3 since the question states you are looking for a 3+ ion. So the electron configuration of a 3+ element is 3d7 4s2. Counting from left to right 7 spots in the d block on the periodic table leads you to Cobalt, giving you an answer of Co3+
b) the same process is repeated here. 3d5 tells you there is 5 electrons, but you need to add an additional 3 for the same reason. So the electron configuration is 3d6 4s2. Counting 6 spots in the d block leads you to Iron, giving you an answer of Fe3+
a) 3d6 tells you there is 6 electrons, but you need to add an additional 3 since the question states you are looking for a 3+ ion. So the electron configuration of a 3+ element is 3d7 4s2. Counting from left to right 7 spots in the d block on the periodic table leads you to Cobalt, giving you an answer of Co3+
b) the same process is repeated here. 3d5 tells you there is 5 electrons, but you need to add an additional 3 for the same reason. So the electron configuration is 3d6 4s2. Counting 6 spots in the d block leads you to Iron, giving you an answer of Fe3+
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