Determining if an atom is in an excited state

[Natalie LeRaybaud 1G]

How can you determine if an atom is in its ground state or excited state just by looking at the electron configuration?

[Hannah Chew 2A]

The electron configurations tell us whether an atom is in an excited state or ground state. In a ground state, electrons fill orbitals to have the lowest energy, so electrons must occupy the lowest orbitals possible. In an excited state, not all electrons are expected to fill the lowest orbitals possible. For example, if ground state is 1s2 2s2 2p1, then an excited state could look like 1s2 2s1 2p2. The difference is that two electrons are in the p orbital in the excited state. This is not the lowest energy configuration because one of the electrons should have been in the 2s orbital to fill the lowest orbital.

[Adrian Lim 1G]

Also, I believe you can look at the different spins on the electron to tell whether it is in an excited state or ground state