As per Pauli’s Exclusion Principle, No two electrons in an atom can have all the four quantum numbers identical or in any orbital maximum number of electrons can be two with opposite spins.
[Know about 4 Quantum numbers & number of orbitals in different subshells]
The maximum number of electrons in :
(i) s subshell can be 2
(ii) p subshell can be 6
(iii) d subshell can be 10
(iv) f subshell can be 14.