posted by David .
Which of the following electron configurations is not consistent with Hund's rule?
1) 1s^2 2s^2 2p^2 3s^1
2) 1s^2 2s^2 2p^6 3s^2 3p^5
3) 1s^2 2s^2 2p^6 3s^3 3p^6
4) 1s^2 2s^2 2px^2 2py^1
Hund's rules has to do with the electrons being paired only when necessary; i.e., after all of the orbitals are half filled, the next electron pairs with one already there. In answering this question, don't confuse Hund's rule with the Aufbau Principle. In other words, don't pick #1 for the correct answer.
I thought it was #3 because there is no
such thing as 3s^3. Am I right?