The Aufbau principle | Atomic structure and properties | AP Chemistry | Khan Academy

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The Aufbau principle states that electrons fill lower-energy atomic orbitals before filling higher-energy ones (Aufbau is German for "building-up"). By following this rule, we can predict the electron configurations for atoms or ions. The Aufbau principle is most useful for the first 20 elements: from Sc on, the Aufbau principle does not accurately predict the order of electron filling in atoms. View more lessons or practice this subject at www.khanacademy.org/science/a...
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[@user-hr2yd3tg2z]

this video has the best explanation so far, hats off to sal

[@helencardrick1048]

You realise you have issues stay up to midnight watching this stuff

[@jasonc.carilla5041]

That's true bro

[@Peugot308]

HAHAHHA YEAH THATD ME😂😂😂

[@loshankosi3119]

now i understand this much better ..thank you so much

[@chloey5418]

thank u I finally understand this :)

[@luce9264]

A little explanation to why positive-charged ions fill in 3d first than 4s: In neutral atom, energy level is as followed by Aufbau principle. In this case: 3d has higher energy level than 4s. However, once the 3d orbital is filled in with electrons, 3d energy level is reduced to lower than 4s. This happens in cations. For this case, 4s has higher energy level than 3d. When removing electrons from atoms to form cations, electrons of higher energy level is removed first. Because in Sc atom 3d is already filled in, its 3d subshell is lesser energy to 4s subshell. Thus, 4s is removed first. tldr: Sc atom has [Ar] 4s^2 and 3d^1, but Sc cation removes 4s subshell first then 3d subshell

[@sciencenerd7639]

it was helpful, thank you

[@angellagman9115]

I got dis thanks 😊❤️

[@luckedout9868]

thaaaaank you so much

[@zack_120]

You should've continued 😀

[@belayethossain2811]

Good

[@PoloML]

for Sc why did you write 3d before 4s? was it intentional or does it not matter?

[@Eren_Yeager_Attack_Titan]

It really doesn't matter. He just represented the orbitals in the order of principle quantum number. It really doesn't matter, all it matters is in which energy level the electron actually lies. But plz don't confuse it when u create an atom from an ion by adding the electrons.(as he mentioned @ 4:54)

[@dharmeshlal7819]

FIRST OF ALL I WOULD HIGHLY RECOMMEND YOU TO WATCH PHYSICS WALLAH AUFBOU PRINCIPLE LECTURE. ITS A SHORT LECTURE . IT WILL JUST TAKE TEN minutes. ITS REALLY HELPFUL

[@sarvagyajain2097]

but pls tell me that if it goes to 3d first so why we study that electron in 4s

[@zenbelt6506]

In calcium why did'nt we put the two electrons in 3d? Please give answer

[@kratos7692]

I'm way too late but its because 4s has lower energy than 3d

[@nakitacoleman13]

@@kratos7692 does that mean we fill in the ones with lower energy first???

[@kratos7692]

@@nakitacoleman13 yes

[@nakitacoleman13]

@@kratos7692 thank you so much that was helpful :)

[@aadityasuralkar5210]

Can anyone tell the electronic configuration of Magnesium (Mn)`

[@mohan1380]

1s^2, 2s^2,2p^6,3s^2

[@NavjotSingh-fv5tj]

(Manganese) Mn 1s2,2s2,2p6,3s2,3p6,3d5,4s2 (Magnesium) Mg 1s2,2s2,2p6,3s2

[@aadityasuralkar5210]

@@NavjotSingh-fv5tj thanks

[@aadityasuralkar5210]

@@mohan1380 Thanks

[@FlareiOS]

Magnesium is Mg, not Mn

[@dorothymukhongo3781]

I got it

[@Michelledesiree33]

Hi

[@melon7538]

Henlow

[@thermonuclearpants553]

yo

[@roser-m8616]

HEYYYYYYY