I had posted the question to that previous chem question, regarding Mo & V...they said that it should have been correct. What I am thinking that I was missing...must have been that I did not include 4s & then just not fill it. I had excluded it from my electron filling altogether. Something the prof said in class a few days after that kind of made me think that that must have been what I was doing incorrectly.

I don't find it and don't remember enough to respond.

It seems like you are referring to a previous question about the electron configuration of Molybdenum (Mo) and Vanadium (V). To clarify, the electron configuration represents the arrangement of electrons within an atom or ion. Each electron occupies an energy level, and within each energy level, there are sublevels that can hold a specific number of electrons.

If you excluded the 4s orbital and did not fill it, that would indeed be an incorrect electron configuration for Mo and V. Both elements follow the Aufbau principle, which states that electrons fill the lowest energy levels first before occupying higher energy levels. In the case of Mo and V, the 4s orbital should be filled before the 3d orbital.

The correct electron configurations are as follows:
- Molybdenum (Mo): 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d⁴
- Vanadium (V): 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d³ 4p⁶ 5s²

To determine the electron configuration on your own, there are a few steps you can follow:
1. Write down the electron configuration of the preceding noble gas. For Mo, the noble gas preceding it is Kr (krypton). For V, the noble gas preceding it is Ar (argon).
2. Fill in the remaining energy levels and sublevels, following the Aufbau principle. Remember that each sublevel can hold a specific number of electrons: s (2 electrons), p (6 electrons), d (10 electrons), and f (14 electrons).

Finally, make sure to double-check your electron configuration and ensure that the total number of electrons matches the atomic number for the element you are studying.