Is the order of filling orbitals the same as the order of increasing energy in orbitals, or is it different?

Please tell me if I am right or wrong:

Order of filling orbitals:
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, etc...

Orbitals in order of increasing energy:
1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p, 4d, 4f, 5s, 5p, 5d, 5f, 6s, 6p, 6d, 6f, etc...

I am pretty sure I got the second one wrong but I am not being able to find an answer anywhere

  • 4
    $\begingroup$ Why would electrons fill in any order except that which minimises energy? The two lists should be (and unless I'm recalling and reading entirely wrongly) and are the same. $\endgroup$
    – Nij
    Nov 10, 2016 at 23:44

1 Answer 1


Energy is the currency of chemistry. If the order in which orbitals fill up and the order in which the energy increases were different, it would mean that that the atom has more energy than it needs. This can happen (the atom is then said to be "excited"), but typically the extra energy distributes into the environment quickly - e.g. by radiating the energy as light - and the atom gets back to the ground state.

That said, the orbital energies are not necessarily the same for all atoms. Getting the correct order is a tricky business, but if you stick to the Aufbau principle (the first ordering you mentioned) you'll be pretty close with the guess. Don't bet on it for d and f elements though.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.