Question

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

• A. There are seven principal electron energy levels
• B. The second principal energy level can have $4$ subenergy levels and contain a maximum of $8$ electrons
• C. The $M$ energy level can have a maximum of $18$ electrons
• D. The $4s$ subenergy level is at a lower energy than the $3s$ subenergy level

Answer 1

The correct option is C The $M$ energy level can have a maximum of $18$ electrons

Principal electron energy levels number are not fixed.

For a maximum electron in energy level is described by $2n^2$ thus for the second shell(L) can have a maximum 8 electrons and third(M) shell have 8 electrons.

According to $n+l$ rule of Aufbau 4s value is 4 and 3s value is 3, thus 4s have higher energy.

Hence, the correct option is $\text{C}$