The number of electrons in the outermost shell of an element with atomic number $15$ is . . . . . . .

Maximum number of electrons theoretically possible for an orbit with principal quantum number $n=6$ in an atom is

Explain,giving reasons,which of the following sets of quantum numbers are not possible.
$(a)$ $n=0, l=0, m_{l}=0, m_{s}=+\frac{1}{2}$
$(b)$ $n=1, l=0, m_{l}=0, m_{s}=-\frac{1}{2}$
$(c)$ $n=1, l=1, m_{l}=0, m_{s}=+\frac{1}{2}$
$(d)$ $n=2, l=1, m_{l}=0, m_{s}=-\frac{1}{2}$
$(e)$ $n=3, l=3, m_{l}=-3, m_{s}=+\frac{1}{2}$
$(f)$ $n=3, l=1, m_{l}=0, m_{s}=+\frac{1}{2}$

The electronic configuration of an element with atomic number $7$ i.e. nitrogen atom is

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

The orbital diagram in which the Aufbau principle is violated is:
$2s$ $2p_x$ $2p_y$ $2p_z$