What is the lowest value of n that allows g orbitals to exist?

Solution:

For $\mathrm{q}$-orbitals, $I=4$.

As for any value ' $n$ ' of principal quantum number, the Azimuthal quantum number $(I)$ can have a value from zero to $(n-1)$.

$\therefore$ For $I=4$, minimum value of $n=5$