## Aufbau Principle - Carbon

Julia Meno 1D
Posts: 28
Joined: Fri Sep 29, 2017 7:04 am

### Aufbau Principle - Carbon

Hi everyone,

Today in lecture Dr. Lavelle used carbon as an example for showing the Aufbau Principle, or the Building-Up Principle.
Here are my notes from it:
Carbon (C)
Z = 6
1s2 2s2 2px1 2py1
2p _
2s

1s
- Add Z e- with no more than 2 e- per orbital (Pauli Exclusion Principle)
- If more than one orbital in a subshell, then add parallel spins to different orbitals (Hund's Rule)

Can someone explain how he formed this electron configuration?

Maeve Gallagher 1J
Posts: 56
Joined: Fri Sep 29, 2017 7:07 am

### Re: Aufbau Principle - Carbon

Hi! To write an electron configuration you first need to know the number of electrons in the atom, which in this case is 6. You then fill the sub shells from lowest to highest, starting with 1s, to 2s, 2p, etc. For carbon, you would first fill the 1s sub shell which can fit 2 electrons, giving 1s^2. Now you have 4 electrons left, and you next fill 2s, which can also hold 2 electrons, giving you 2s^2. Finally, you start to fill 2p with the 2 remaining electrons you have, putting one into the px orbital and one into the py. This will give you 2px^1 2py^1. Now you've used up all of carbon's electrons, so you can put it all together to get 1s^2 2s^2 2px^1 2py^1. Hope that helps!

Sophia Kim 1C
Posts: 51
Joined: Fri Sep 29, 2017 7:04 am
Been upvoted: 1 time

### Re: Aufbau Principle - Carbon

You use the number of electrons and start from the lowest subshell to the highest! So first in the example, carbon has 6 electrons so for the first subshell s, it holds two electrons so its 1s2 and then the next is 2s which also holds 2 electrons so its 2s2 and so with the remaining two electrons you fill 2p and one goes to the orbital px and one goes to py so its 2px and 2py. combining that all together gets 1s2 2s2 2px 2py