For #"iron"#, #Z=26#, and thus for elemental iron we have to distribute 26 electrons by the aufbau scheme, and for #Fe^(3+)#, we must distribute 23 electrons..................And so:
#1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)3d^(5)#.
Note that a neutral iron atom has a configuration of.......
#1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)4s^(2)3d^(6)# (26 electrons as required.) However, upon oxidation, the #4s# electrons are conceived to be removed FIRST, and this is typical for transition metal ions.
Would #Fe(III)# complexes be paramagnetic? Why or why not........?
