Well, I was doing this problem:
Write the el. configuration of an atom, if his valent electrons have these properties:
n=4, l=0, ml=0, ms=+1/2
n=4, l=0, ml=0, ms=-1/2
n=4, l=1, ml=0, ms=+1/2
I thought that the configuration of the valent electrons would be: 4s2 4p2, but in the answer it is 4s2 4p1. I am really confused. How can that be right?