OCR A level chemistry electron configuration HELP (Ga3+) Watch

username5002602
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This question is from the OCR A level chemistry oxford textbook (chapter 5)

eii) write the electron configuration of Ga3+
my answer: 1s2 2s2 2p6 3s2 3p6 4s2 3d8

mark scheme: 1s2 2s2 2p6 3s2 3p6 3d10

I'm assuming the mark scheme answer above is because Ga3+ lost 3 electrons from (4s2 + 4p1) but i though 4s has a lower energy level than 3d so aren't electrons removed from 3d first. Also, in this book on page 58, it has a study tip of " 4s electrons are first in and first out".

Can somebody help?
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emma64
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Electrons are removed from 4s sub shell before the 3d (due to reasons we don’t need to know about at alevel) 4s subshells are “first in and first out” because they are filled before the 3d, but also 4s electrons are removed before 3d electrons are. It’s just one of those things we have to learn!
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Huckipity
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(Original post by 20alevel20)
This question is from the OCR A level chemistry oxford textbook (chapter 5)

eii) write the electron configuration of Ga3+
my answer: 1s2 2s2 2p6 3s2 3p6 4s2 3d8

mark scheme: 1s2 2s2 2p6 3s2 3p6 3d10

I'm assuming the mark scheme answer above is because Ga3+ lost 3 electrons from (4s2 + 4p1) but i though 4s has a lower energy level than 3d so aren't electrons removed from 3d first. Also, in this book on page 58, it has a study tip of " 4s electrons are first in and first out".

Can somebody help?
Gallium's electron configuration is 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p1. If we remove 3 electrons from this, knowing that 4s is removed first over the 3d oribtal (due to it having more energy) we get 1s2, 2s2, 2p6, 3s2, 3p6, 3d10
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Pigster
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(Original post by emma64)
4s subshells are “first in and first out” because they are filled before the 3d
That isn't quite true.
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emma64
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(Original post by Pigster)
That isn't quite true.
Oh really, thats what we are taught at a level. How does it work then? (not doubting you, just curious as I want to do a biochem degree )
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Pigster
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(Original post by emma64)
Oh really, thats what we are taught at a level. How does it work then? (not doubting you, just curious as I want to do a biochem degree )
Try this: http://ericscerri.blogspot.com/2012/...u-to-find.html
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emma64
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Thank you! It’s such a shame that everything gets oversimplified at a level, leading to a lot of misconceptions.
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