Question

Which of the following sets of quantum numbers could possibly describe an electron in the ground-state configurations of beryllium. Choose all that apply (e.g. AB, ABC, ABDF).

A) n=1 l=0 ml=0 ms=1/2
B) n=3 l=1 ml=-1 ms=1/2
C) n=2 l=0 ml=0 ms=-1/2
D) n=2 l=1 ml=0 ms=1/2
E) n=3 l=2 ml=0 ms=1/2
F) n=2 l=1 ml=1 ms=-1/2
Which of the above sets of quantum numbers could possibly describe an electron in the ground-state configurations of sodium. Choose all that apply (e.g. AB, ABC, ABDF).

Answer 1

These usually are confusing for students; the secret is to follow the rules.
4Be is 1s2 2s2.
For the 1s2 n = 1, s means l = 0 and there is 1electron with +1/2 and the other with -1/2. You simply go down the choices and pick any that has n = 1, l = 0, ml = 0 and ms = +/- 1/2. No others will do. A choice will do that.

For the 2s2 n = 2, s means l = 1 and again 1 electron has +1/2 and the other -1/2. Go through the choices again and look for n = 2, l = 0, ml = 0, ms = +/- 1/2. C choice will do that.
B can't because there is no n = 3
D no because there is no l > 0. Same for F.
E can't; there is no n = 3.

Now you do the Na the same way.
This should get you started.
11Na = 1s2 2s2 2p6 3s1