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### ground state electron configurations

Posted: Wed Oct 23, 2019 10:39 pm
can someone please explain this problem? i didn't really understand any part of it

2A.11 Which M3+ ions (where M is a metal) are predicted to have the following ground state election configurations: (a) [Ar] 3d6; (b) [Ar] 3d5; (c) [Kr] 4d5; (d) [Kr] 4d3

thanks

### Re: ground state electron configurations

Posted: Wed Oct 23, 2019 10:56 pm
I think this question can be solved by looking at a periodic table.

(a) [Ar] 3d6 :
No. of electrons in M ^+3 state = 18 + 6 = 24
Therefore no. of electrons in M = 24 + 3 = 27
Therefore M is Co

(b) [Ar] 3d5 :
No. of electrons in M^+3 state = 18 + 5 = 23
Therefore no. of electrons in M = 23 + 3 = 26
Therefore M is Fe

(c) [Kr] 4d5 :
No. of electrons in M^+3 state = 36 + 5 = 41
No. of electrons in M = 41 + 3 = 44
Therefore M is Ru

(d) [Kr] 4d3 :No. of electrons in M^+3 state = 36 + 3 = 39
No. of electrons in M = 39 + 3 = 42
Therefore M is Mo

### Re: ground state electron configurations

Posted: Wed Oct 23, 2019 11:30 pm
If it is in a plus 3 state, shouldn't we subtract 3 electrons instead of add?

### Re: ground state electron configurations

Posted: Thu Oct 24, 2019 12:04 am
I’m also confused as to why we add instead of subtracting 3.