Using the normal notation of quantum number find the element which has the following value of quantum number
n=3 l=2 m=2 s=+1/2
(a):potassuim
(b):nitrogen
(c):sodium
(d):scandium
Is that the last electron, the single electron, the outside electron. I assume it's the single electron. Go through each one this way.
19K = 1s2 2s2 2p6 3s2 3p6 4s1
For the 4s1 electron, n = 4 so it can't be K. Also note that s electrons have l = 0; another reason it can't be K.
7N = 1s2 2s2 2p3
n is 2 and l is 1 so it can't be N.
11Na = 1s2 2s2 2p6 3s1
n = 3 but l = 0 so can't be Na.
Check out Sc
21Sc=1s2 2s2 2p6 3s2 3p6 4s2 3d1