Question

For each electron in a ground-state Be atom, select the set of quantum numbers that represents it. Check all that apply.

n=1 l=0 ml=-1 ms= +1/2
n=1 l=0 ml=0 ms=-1/2
n=2 l=1 ml=0 ms= -1/2
n=1 l=0 ml=0 ms=+1/2
n=2 l=1 ml=1 ms=+1/2
n=2 1=0 ml=0 ms=+1/2
n=2 l=0 ml=0 ms=-1/2
n=2 l=0 ml=0 ms=-1

I know the top one and the last one aren't correct but I don't know about the others. The hint said,"Make sure you have chosen exactly four answers" why will it have 4?

Answer 1

There are four electrons, right? So there must be four answers.
#1 electron:
n = 1
l = 0
ml = 0
ms = +1/2

#2 electron:
n = 1
l = 0
ml = 0
ms = -1/2
That's two of them.

#3 electron:
n = 1
l = 0 or 1
ml = etc
All you really need to do is to fill in the blanks as the electrons are added. I've done the two n= 1 electrons, There are now two n = 2 electrons and another hint: l = 0 fills up first.

You're right about the top one and last one not being right.