When the azimuthal quantum number has a value of $l = 0$,the shape of the orbital is

How many orbitals is/are possible with $n=3$,$l=1$ and $m_l=-1$ values?

If an atom has $13$ electrons in the $M$ shell and $1$ electron in the $N$ shell,then the number of unpaired electrons in that atom is ...

What is the maximum number of electrons that can be accommodated in a shell with principal quantum number $n = 4$?

Which of the following shows half-filled configuration?

Identify the correct statements:
a) In an atom,the maximum number of electrons with $n=4$ and $m_s=+\frac{1}{2}$ is $16$.
b) There are $4$ subshells associated with $n=5$.
c) $n=2, l=1, m_l=0$ and $m_s=-\frac{1}{2}$ is a possible set of quantum numbers.
d) The number of radial nodes for $3s$ orbital is $2$.