Question: n=5 ms=+1/2 how many electrons?
Answer: The fast way to do it is also to use the relation that the number of orbitals within the n shell of electrons is n^2. So for principle quantum number n=5, there are 25 orbitals, and only 1 electron within each orbital can have a value ms= +1/2, meaning there are 25 electrons with n=5 and ms= +1/2.