Show that an orbital cannot accommodate more than two electrons in it.

Explanation

Each electron present inn an atom is expressed by four quantum numbers. Again, according to Pauli's exclusion principle, no two electrons in an atom can have same values for all the four quantum numbers `(n,l,m and s)`.
Now for a certain orbital, the quantum numbers n, l and m have definite values. so, the electrons present in the orbital must have different values for the spin quantum number. but the spin quantum number 's' has only two possible values. these are `+(1)/(2) and -(1)/(2)`. hence, the maximum no. of electrons that can be accomodate in an orbital is 2. for example, values of the quantum number of two electrons in 1s-orbital are as follows-
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