In an element with atomic number $(Z) = 25$,the number of electrons with $(n+l)$ value equal to $3$ and $4$ are $x$ and $y$ respectively. The value of $(x+y)$ is

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

In the ground state, an element has $13$ electrons in the $M$ shell. The element is

Which set of quantum numbers for an electron of an atom is not possible?

Which among the following species has the same number of electrons in its outermost as well as penultimate shell?

The number of radial nodes of $3s$ and $2p$ orbitals are respectively.