The maximum number of electrons in a subshell is given by the expression:

Which of the following elements are exceptions to the $(n + l)$ rule?

Identify the incorrect statement from the following:

In a multi-electron atom,which of the following orbitals have the same energy in the absence of magnetic and electric fields? $(a) n = 1, l = 0, m = 0, (b) n = 3, l = 0, m = 0, (c) n = 2, l = 1, m = 1, (d) n = 3, l = 2, m = 1, (e) n = 3, l = 2, m = 0$

Two statements are given below:
Statement $I$: In $H$ atom, the energy of $2s$ and $2p$ orbitals is same.
Statement $II$: In $He$ atom, the energy of $2s$ and $2p$ orbitals is same.
The correct answer is:

What is the number of unpaired electrons in a ferrous ion $(Fe^{2+})$?