How many electrons in a cesium atom can have the quantum numbers of n = 3 and ml = -1

Answer 1

If n = 3, then
l = 0, 1...and .........2
ml = 0|-1,0,+1|...-2.-1,0,+1,+2
ms = 2 electrons in each
You have two possible -1 values for m; (that's with l = 1 and l = 2. You have two electrons (ms = +/- 1/2 with each) so you can have four electrons.