49


ANSWER……


ELEMENT ATOMIC NUMBER SUBSHELL ELECTRONIC CONFIGURATION THE SUBSHELL TO WHICH THE LAST ELECTRON IS ADDED BLOCK
3Li 3 1S2 2S1 s S
12Mg 12 1S2 2S2 2P6 3S2 s s
7N 7 1S2 2S2 2P3 p p
21Sc 21 1S2 2S2 2P6 3S2 3p6 3d1 4s2 d d