The maximum number of electrons that can have the set of quantum numbers $n=4$,$m_l=0$,and $m_s=\frac{1}{2}$ is

The number of unpaired electrons in $1s^2 2s^2 2p^3$ is:

The probability of finding an electron in the $d_{xy}$ orbital is maximum along:

Which of the following statements is $FALSE$?

The number of unpaired electrons in $Fe^{3+}$ $(Z = 26)$ is:

The hydrogen-like species $Li^{2+}$ is in a spherically symmetric state $S_1$ with one radial node. Upon absorbing light,the ion undergoes transition to a state $S_2$. The state $S_2$ has one radial node and its energy is equal to the ground state energy of the hydrogen atom.
$1.$ The state $S_1$ is
$(A)$ $1s$ $(B)$ $2s$ $(C)$ $2p$ $(D)$ $3s$
$2.$ Energy of the state $S_1$ in units of the hydrogen atom ground state energy is
$(A)$ $0.75$ $(B)$ $1.50$ $(C)$ $2.25$ $(D)$ $4.50$
$3.$ The orbital angular momentum quantum number of the state $S_2$ is
$(A)$ $0$ $(B)$ $1$ $(C)$ $2$ $(D)$ $3$
Give the answer for questions $1, 2$ and $3.$