Answer:
3 (s,p,d)
Explanation:
Principle energy levels number of sublevels number of electrons
1 1s 2n² = 2(1)²= 2
2 2s 2n² = 2(2)²= 8
2p
3 3s 2n² = 2(3)²= 18
3p
3d
when an atom has 3 energy level it has 1 sublevel (s) in 1st energy level 2 sublevels (s ans p) in second energy and three sublevels in third energy level (s,p,d). This atom with n=3 can accommodate 18 electrons in these sublevels.
