What is the maximum number of electrons which can be accommodated in an atom in which the highest principal quantum number value is $4$?

The five valence electrons of $P^{15}$ are labeled as $A, B, X, Y, Z$ as shown in the figure. If the spin quantum number of $B$ and $Z$ is $+\frac{1}{2}$,identify the group of electrons that share three identical quantum numbers.

The atomic number of an element is $35$ and its mass number is $81$. The number of electrons in the outermost shell is:

What is the electronic configuration of $Cu$?

The energy of orbitals in a hydrogen atom can be determined by which of the following quantum numbers?

The maximum number of electrons in an atom in which the last electron filled has the quantum numbers $n=3, \ell=2$ and $m=-1$ is