Electron Configurations

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Abby Ellstrom 1I
Posts: 53
Joined: Fri Sep 29, 2017 6:04 am

Electron Configurations

Postby Abby Ellstrom 1I » Wed Nov 01, 2017 4:30 pm

Which M2+ ions (where M is a metal) are predicted to have the following ground-state electrons:
(a) [Ar]3d7
(b) [Ar]3d6

The answer to
(a) is Co2+
(b) is Fe2+

I am just very confused as to where these answers came from.

Emma Boyles 1L
Posts: 19
Joined: Thu Jul 27, 2017 2:00 am

Re: Electron Configurations

Postby Emma Boyles 1L » Wed Nov 01, 2017 6:21 pm

In both cases, electrons will be taken from the 4s orbital first because the 4s orbital actually has a lower energy level than 3d. It is easier to remove an electron from the 4s orbital than the 3d orbital.

Therefore, the metals would stay Co and Fe but acquire a 2+ charge.

Ethan Mondell 1A
Posts: 20
Joined: Fri Sep 29, 2017 6:04 am
Been upvoted: 1 time

Re: Electron Configurations

Postby Ethan Mondell 1A » Wed Nov 01, 2017 8:34 pm

Normally the following electron configurations would be accurate

Co: [Ar] 3d7 4s2
Fe: [Ar] 3d6 4s2

Since the electron configurations that were given to us both were missing the 4s orbital yet had electrons in the 3d orbital, we can infer that the electron configurations must be those of cations because normally the 4s orbital is filled before the 3d orbital. Since there is no 4s orbital, 2 electrons must have been taken from that orbital because electrons are lost from higher energy levels before lower energy levels (n=4>n=3). Now you can just look figure out which two elements had their valence electrons as the 3d7 and 3d6 and then use those 2 elements (Co and Fe) and make them cations with a +2 charge.

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