For the energy levels in an atom , which one of the following statement is 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 enerty than the 3d sub energy level.

Answer

A, D

Explanation

A and D are true B is wrong because for `n=2, l=0, 1` (two sub enerty levels). (C) is wrong because M shell means n=3. Maximum electrons it can have `=2n^(2)=2xx3^(2)=18`
Hence A and D is the correct answer.