Aufbau Principle: it states that atomic orbitals are filled by electrons in order of increasing energies (according to n+1 rule)
Hund‘s rule: Pairing of electrons in degenerate orbitals take place only after each orbital is filled in with single electron with same spin.
Pauli‘s exclusion Principal: No two electrons in an atom have all the four quantum numbers same. Or An orbital can accommodate a maximum of two electrons of opposite spin. Heisenberg‘s Uncertainty Principle: It is impossible to determine simultaneously the exact position & momentum of a microscopic particle like electron.
