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

Answered below.

I thought #3 was the answer because there is no such thing as 3S^3 right?

To determine which electron configuration is not consistent with Hund's rule, we need to understand what Hund's rule states.

Hund's rule states that when filling orbitals of the same energy (degenerate orbitals), electrons will first occupy empty orbitals singly before pairing up. This occurs to maximize the number of unpaired electrons and make the configuration more stable.

Now, let's analyze each option:

1) 1s^2 2s^2 2p^2 3s^1
This configuration is consistent with Hund's rule because in the 2p sublevel, there are two electrons in two different orbitals with the same spin before pairing up.

2) 1s^2 2s^2 2p^6 3s^2 3p^5
This configuration is consistent with Hund's rule. All the orbitals are filled with electrons having the same spin before any pairing occurs.

3) 1s^2 2s^2 2p^6 3s^3 3p^6
This configuration is consistent with Hund's rule as well. All the orbitals in the 3s and 3p sublevels are filled up before any pairing occurs.

4) 1s^2 2s^2 2px^2 2py^1
This configuration is not consistent with Hund's rule. According to Hund's rule, the 2px orbital should have only one electron with one spin before pairing occurs. However, in this configuration, the 2px orbital has two electrons, violating Hund's rule.

Therefore, the option that is not consistent with Hund's rule is:
4) 1s^2 2s^2 2px^2 2py^1