# Pauli's Exclusion Principle

While reading Pauli's Exclusion principal from here, they said that

The Pauli Exclusion Principle states that, in an atom or molecule, no two electrons can have the same four electronic quantum numbers." Now again in we know that the The orbital angular momentum quantum number $l= 0,1,2... (n-1)$ – Source

So from here we can say that $l\neq n$. So here automatically no two electrons can have the same four quantum numbers. So what's new in Pauli's principle?

I think you've misunderstood, Pauli's exclusion principle doesn't mean that the four numbers are different it means that no electron can have the same respective values for $n$, $l$, $m_s$, $m_l$ as another electron (in some case some of the numbers themselves can be the same). i.e. electrons in the same suborbital must have different spins.
• $n$ indicates the orbital shell
• $l$ indicates the type of suborbital, s, p etc
• $m_l$ indicates the orientation of the suborbital, px, py etc
• $m_s$ indicates the electron spin
Pauli's exclusion principle means that no electron around an atom can occupy identical orbitals, i.e two electron with up spin in a 2s1, as all their electron numbers would be the same as their respective equivalents ($n_1 =n_2 = 2$, $l_1 = l_2 = 0$, $m_{l,1} = m_{l,2} = 0$, $m_{s,1} = m_{s,2} = -1/2$).