The total maximum number of electrons possible in $3d$,$6d$,$5s$,and $4f$ orbitals with $m_l$ (magnetic quantum number) value $-2$ is

Which of the following statements are correct?
$(a)$ When an electron in an atom moves from $n=4$ to $n=2$,it gains energy.
$(b)$ An electron in a $3p$ orbital would have less energy than an electron in a $2p$ orbital.
$(c)$ $A$ $3s$ subshell has a maximum of $2$ electrons.
$(d)$ $A$ $3^{rd}$ orbit may contain a maximum of $10$ electrons.

The quantum numbers of four electrons are given below:
$I. \ n = 4, l = 2, m_l = -2, m_s = -1/2$
$II. \ n = 3, l = 2, m_l = 1, m_s = +1/2$
$III. \ n = 4, l = 1, m_l = 0, m_s = +1/2$
$IV. \ n = 3, l = 1, m_l = 1, m_s = -1/2$
The correct order of their increasing energies will be:

What is the number of unpaired electrons present in $d$ orbitals of $Cr (Z=24)$ to have extra stability?

Which one of the following sets of quantum numbers is incorrect?

Principal quantum number $(n)$	Azimuthal quantum number $(l)$	Magnetic quantum number $(m)$

The number of orbitals in the fourth principal quantum number $(n = 4)$ is: