In which species would 2 unpaired electrons be present in the ground state: #"a. sodium atom;"# #"b. cobalt atom;"# #"c. iron dication,"# #Fe^(2+)#; #"d. iron atom?"#

1 Answer
anor277
Aug 16, 2017

#"Option (d)"#.

Explanation:

We can immediately eliminate #Na#, #Z=11#, and #Co#, #Z=27#, because these give rise to an odd number of electrons in the ground state, the which must necessarily be UNPAIRED.

As regards, #b.#, i.e. #Fe#, we have #Z=26#, however, Hunds' rule dictates a configuration of #1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)4s^(2)3d^6#. In the isolated ATOM, we must fit 6 electrons into the 5 valence #"d-orbitals"#. At least 2 of the electrons must be unpaired.

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