electron config

when writing the electron configuration which is written first, the 3d or 4s. stupid question but I've seen it written in both ways so its really confused me as to whether its 3d 4s or 4s 3d

Reply 1

SChampion

Original post by sg.0

when writing the electron configuration which is written first, the 3d or 4s. stupid question but I've seen it written in both ways so its really confused me as to whether its 3d 4s or 4s 3d

It honestly does not matter - out of principle, I would always write 3d first. But it's your choice!

Reply 2

Methene

I've learnt writing it as 4s followed by 3d, in the same order that they fill with electrons. But I did AQA chemistry and it could be different for other exam boards, so best to check either directly on the spec or with your teacher. As above, probably doesn't matter in the big picture...

Reply 3

SChampion

Original post by Methene

Your username would make most chem teachers cry 😭😭

Reply 4

Idk5677

Original post by sg.0

when writing the electron configuration which is written first, the 3d or 4s. stupid question but I've seen it written in both ways so its really confused me as to whether its 3d 4s or 4s 3d

The 4s fills up before 3d however the exceptions are Chromium and Copper. Also when the atoms lose electrons the 4s empties out first

Reply 5

Jam.123

Original post by sg.0

when writing the electron configuration which is written first, the 3d or 4s. stupid question but I've seen it written in both ways so its really confused me as to whether its 3d 4s or 4s 3d

You should be writing 3d 4s even though order of filling is different

Reply 6

Methene

Original post by SChampion

Your username would make most chem teachers cry 😭😭

Haha agreed 😁

Reply 7

UtterlyUseless69

Original post by sg.0

when writing the electron configuration which is written first, the 3d or 4s. stupid question but I've seen it written in both ways so its really confused me as to whether its 3d 4s or 4s 3d

It can be done either way, but out of principle, I would usually write it as 4s 3d, since 3d fills after 4s.

However, for illustrative purposes when I used to mentor A level chemistry (e.g showing how the electrons are removed in transition metals) I often wrote 3d 4s as the 4s electrons are removed first and it makes sense to list all the subshells in the order in which electrons would be removed from them.

Reply 8

UtterlyUseless69

Original post by SChampion

Your username would make most chem teachers cry 😭😭

Most, perhaps. The H2C: carbene, although systematically called methylidene is often called methene. And yes, it is an actual thing - it’s a known intermediate in certain decomposition reactions and not just some molecule dreamed up by computational chemists.