The electronic configuration of the element with atomic number $24$ is:

The number of radial nodes of $3s$ and $2p$ orbitals are respectively.

The quantum numbers of six electrons are given below. Arrange them in order of increasing energy. If any of these combinations have the same energy,list them:
$(1)$ $n = 4, l = 2, m_l = 2, m_s = -1/2$
$(2)$ $n = 3, l = 2, m_l = 1, m_s = +1/2$
$(3)$ $n = 4, l = 1, m_l = 0, m_s = +1/2$
$(4)$ $n = 3, l = 2, m_l = -2, m_s = -1/2$
$(5)$ $n = 3, l = 1, m_l = -1, m_s = +1/2$
$(6)$ $n = 4, l = 1, m_l = 0, m_s = +1/2$

The number of $d-$ electrons in $Fe^{2+} \ (Z = 26)$ is not equal to the number of electrons in which one of the following?

The number of electrons that can be present in sub-shells having $m_s$ value of $\frac{-1}{2}$,for $n$ up to $3$.

How many electrons can a given orbital accommodate?