State and explain Pauli's exclusion principle. 

Explanation

Pauli.s exclusion principle: According to this principle "No two electrons in an atom.can have the same set of four quantum numbers". This can also be . stated as "only two electrons. may exist in the same orbital. and these electrons must have opposite spins".
This means that the two electrons can have the same value of three quantum numbers n,l and `m_(l)`. but have the opposite spin quantum number Ex : Consider .K. shell of the atom having two electrons
`{:("Electron",n,l,m,s),(1^(st)" electron",1,0,0,+(1)/(2)),(2^(nd)" electron",1,0,0,-(1)/(2)):}`