work out the number of unpaired electrons in the ground states of the following ions: 1)La3+ 2)Yb2+

work out the number of unpaired electrons in the ground states of the following ions: 1)La3+ 2)Yb2+

Grade:Upto college level

1 Answers

Aman Bansal
592 Points
10 years ago

Dear Bipasha,

"Shells" are composed of individual orbitals. The valence shell is the outer most shell and only its s and p orbitals are occupied, which is why the octet rule works.

As elements need to accommodate more electrons, they fill empty orbitals in inner shells. Inner shells have these orbitals ALWAYS, whether they are occupied or not:

1st shell (s)
2nd shell (s,3p)
3rd shell (s, 3p, 5d)
4th shell (s, 3p, 5d, 7f)
5th shell (s, 3p, 5d, 7f) (there is no need for further orbitals)
5th shell (s, 3p, 5d, 7f) 

s,p,d,f orbitals are ALL separate; except when "hybridized"!

Hund's rule states that in filling an orbital group, e's remain un-paired until they HAVE TO start doubling up.

1-e in the valence shell (s1 p0 - 1 unpaired)
2-e's in the valence shell (s2 p0 - 0 unpaired)
3-e's in the valence shell (s2 p1 - 1 unpaired)
4-e's in the valence shell (s2 p2 - 2 unpaired)
5-e's in the valence shell (s2 p3 - 3 unpaired)
6-e's in the valence shell (s2 p4 - 2 unpaired)
7-e's in the valence shell (s2 p5 - 1 unpaired)
8-e's in the valence shell (s2 p6 - 0 unpaired)

Best Of luck

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Aman Bansal

Askiitian Expert

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