2. 39 [ENDORSED]

[Juanalv326]

2.39 Determine whether each of the following electron confi gurations represents the ground state or an excited state of the atom given.

What are the explanations and how would you do this?

[Tanaisha Italia 1B]

In order for the atom to be shown in its ground state, the number of arrows/the direction they are facing/how they are spaced must all be correct. For part a, the number of arrows (6 - the atomic number of Carbon) is correct, but the two arrows in 2p should be in two separate boxes and should be facing the same way (up). It is easier for them to go into separate orbitals, even though the first box is not filled yet. Going into separate boxes/orbitals also accounts for why they should have a parallel spin (both arrows facing the same direction). Thus, part a is not in its ground state because the arrows are spaced differently and are facing opposite directions. For part b, the arrow in the middle box for 2p is facing in the opposite direction, which should not happen since the electrons are in separate orbitals and should all be facing the same direction (parallel spin). For part c, there is an arrow in the box for 2p, but the orbital for 2s has not yet been filled with two electrons. The atom cannot move up to 2p unless it has filled the 2s orbitals or the atom has been excited (increased in energy). Thus, the atom is in an excited rather than a ground state. Part d is the only option which shows the right number, direction, and spacing of arrows in the electron configuration.

[Kelly Kiremidjian 1C]

I had the same question....so you can determine wether the electron is in the excited state or not by seeing if it correctly spaced in the boxes?

[Chem_Mod]

Yes you can. If it is not in the normal configuration, it means the electron is excited.

[104754311]

For part a, so is it better to have incomplete p orbitals than pair the two electrons into one? Can someone explain why that is?

[904914909]

So lowest energy configuration means that an atom is in ground state and anything else is excited?