Energy of Orbitals

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Amelia Vernon 2L
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Joined: Fri Sep 25, 2015 3:00 am

Energy of Orbitals

Postby Amelia Vernon 2L » Fri Oct 16, 2015 2:29 am

Since 4s fills up first, does that mean that the 3d has less energy?

For example, with Potassium, the 4s orbital is slightly less in energy, which is why it fills up first, but why is the 3d written before the s orbital in the electron configuration? Doesn't that imply that the 3d is less in energy? Or does that change?

Brooke Tobias 1B
Posts: 13
Joined: Fri Sep 25, 2015 3:00 am

Re: Energy of Orbitals

Postby Brooke Tobias 1B » Fri Oct 16, 2015 9:33 am

In the course reader, it states that "once 4s orbital is filled and e- enter 3d-orbitals, then 3d-orbitals become lower in energy than 4s." I believe that the electron configuration is the order in which the electrons are filled, but in actuality, the valence electrons are always in the outermost shell (so whichever electrons have the highest principal quantum number)? And I think it is rewritten this way to reflect that, maybe.

anne_kleinaitis_3B
Posts: 13
Joined: Fri Sep 25, 2015 3:00 am

Re: Energy of Orbitals

Postby anne_kleinaitis_3B » Fri Oct 16, 2015 3:04 pm

I was confused on this topic too. This website explains in detail:

http://chemwiki.ucdavis.edu/Inorganic_C ... s_Orbitals

Basically, 4s is let go first. P and S are always let go before D when dropping an electron. The rule of halves explains why some fill 3d before 4s. Check out the above website, I promise it helps!


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