Hello aspirant,

Hope you are doing well

Hund's Rule states that if 2 or more degenerate (i.e. same energy) orbitals are available, one electron goes into each until all of them are half full before pairing up .

Or we can say that Every orbital in a subshell is singly occupied with one electron before any one orbital is doubly occupied and all electrons in singly occupied orbitals have the same spin.

For example-You may have heard this one in relation to the analogy of filling seats in a bus; everyone finds their own seat, and only when all the seats are half full do they start sitting together.

The Pauli Exclusion Principle states that no two electrons can be identified by the same set of quantum numbers . This is actually why we have the spin quantum number, ms , to ensure that two electrons within the same orbital have unique sets of quantum numbers.

Or we can say that:-

The Pauli Exclusion Principle states that, in an atom or molecule, no two electrons can have the same four electronic quantum numbers. ... Electrons in the same orbital have the same first three quantum numbers, e.g., n=1n=1, l=0l=0, ml=0ml=0 for the 1s subshel

Hope this helps you

Feel free to ask any questions

All the best for your future