What is the number of $d$-electrons present in $Fe^{2+}$ ($Fe$ atomic number = $26$)?

The orbital angular momentum of an electron in $2s$ orbitals is

Which of the following orbitals is represented by $n=3$ and $l=2$?

Consider the following statements:
$(a)$ Electron density in the $XY$ plane in $3d_{x^2-y^2}$ orbital is zero.
$(b)$ Electron density in the $XY$ plane in $3d_{z^2}$ orbital is zero.
$(c)$ $2s$ orbital has one nodal surface.
$(d)$ For $2p_z$ orbital,$YZ$ is the nodal plane.
Specify True or False.

Which of the following orbitals is not possible (in $f$)?

$(i)$ Write the electronic configurations of the following ions:
$(a)$ $H^{-}$
$(b)$ $Na^{+}$
$(c)$ $O^{2-}$
$(d)$ $F^{-}$
$(ii)$ What are the atomic numbers of elements whose outermost electrons are represented by
$(a)$ $3s^{1}$
$(b)$ $2p^{3}$ and
$(c)$ $3p^{5}$?
$(iii)$ Which atoms are indicated by the following configurations?
$(a)$ $[He] 2s^{1}$
$(b)$ $[Ne] 3s^{2} 3p^{3}$
$(c)$ $[Ar] 4s^{2} 3d^{1}$