The number of unpaired electrons in $Ni$ (atomic number $= 28$) is:

Which of the following is the correct electronic configuration?

In a chromium atom,the number of electrons which have $n = 2$ and $l = 1$ is:

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:

Maximum number of electrons in a subshell with $n=4$ and $l=3$ is

The graph showing the variation of probability density,$\psi^2(r)$ with the distance of the electron from the nucleus,$r$ is given below. This represents: