Question

# Pauli’s exclusion principle states that:(a)- The nucleus of an atom is negatively charged.(b)- Electrons enter into lowest-energy orbitals.(c)- Electrons revolve around the nucleus in circular orbits.(d)- No two electrons in an atom can have all the four quantum numbers the same.

Now, any particular orbital is described by three quantum numbers i.e. n, l, and m. For example, 3s-orbital has $n=3,l=\text{0 and }m=0$.since for each value of m, there are two values of the spin quantum number, i.e., $+\dfrac{1}{2}$ and $-\dfrac{1}{2}$ , therefore, 3s-orbital can have two electrons; one with quantum numbers $n=3,l=\text{0, }m=\text{0 and }s=+\dfrac{1}{2}$, and the other with quantum numbers, $n=3,l=\text{0, }m=\text{0 and }s=-\frac{1}{2}$.