For the energy levels in an atom, which one of the following statement(s) is (are) correct ?

Options

A. There are seven principal electron energy levels
B. The second principal energy level can have four sub-energy levels and contain a maximum of eight electrons
C. The M energy level can have a maximum of 32 electrons
D. The 4s sub-energy level is at a lower energy than the 3d sub-energy level.

Answer

A, D

Explanation

a) and d) are true.
b) is wrong because for m = 2. l=0 ,1 (two sub-energy levels).
c) is wrong because M shell means n =3 . Maximum electrons it can have = `2n^2= 2 xx 3^2 = 18`