Which of the following is/are not correct with respect to energy of atomic orbitals of hydrogen atom?
$A$. $1s < 2p < 3d < 4s$
$B$. $1s < 2s = 2p < 3s = 3p$
$C$. $1s < 2s < 2p < 3s < 3p$
$D$. $1s < 2s < 4s < 3d$
Choose the correct answer from the options given below:

Which of the following is the correct plot for the probability density $\psi^{2}(r)$ as a function of distance '$r$' of the electron from the nucleus for $2s$ orbital?

Which electronic arrangement shows the ground state of an element?

Given below are two statements. One is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$ : Energy of $2s$ orbital of hydrogen atom is greater than that of $2s$ orbital of lithium.
Reason $R$ : Energies of the orbitals in the same subshell decrease with increase in the atomic number.
In the light of the above statements,choose the correct answer from the options given below.

Which of the following are correct?
$(1)$ Electron density in $XY$ plane for $d_{x^2-y^2}$ orbital is zero.
$(2)$ The energy of $3p$-orbital is higher than the energy of $2p$-orbital.
$(3)$ $3p_z$-orbital has one angular node.
$(4)$ $4f$-orbital has no radial node.

The total number of electrons present in all the $s$-orbitals,all the $p$-orbitals,and all the $d$-orbitals of the cesium ion $(Cs^+)$ are respectively: