## Building Up Principle [ENDORSED]

$sp, sp^{2}, sp^{3}, dsp^{3}, d^{2}sp^{3}$

Ronica_Patel_3G
Posts: 10
Joined: Sat Jul 09, 2016 3:00 am

### Building Up Principle

In the course reader, there was an example pertaining to the Building Up Principle. It was given that Z=6 and (1s^2)(2s^2)(2px^1)(2py^1). In the periodic table, it says (2s^2)(2p^2). I don't understand how the 2p^2 got split into (2px^1)(2py^1). Can someone explain it? Thanks.

Yuchien Ma 2L
Posts: 46
Joined: Wed Sep 21, 2016 2:58 pm

### Re: Building Up Principle  [ENDORSED]

Electrons naturally repel each other, so they will fill up the empty orbitals before they fill up the already filled ones.
Think of it like pairs of bus seats...you will sit in an empty pair of seats if you can. You will only sit with a stranger if there are no empty pairs of seats left, and you absolutely have to.
Therefore, electrons will first fill up the 2px, then the 2py, and then the 2pz. The next electron will go into the 2px orbital because there are no other empty orbitals left.
This is called Hund's rule.
Hope this helps.