The energy difference between the following two successive levels is minimum

$\mathrm{Energy}\infty \frac{1}{{\mathrm{n}}^2}$

On increasing the value of n (orbit number), energy decreases. For n=1, energy is maximum and for n=5, energy is minimum. Hence, the maximum energy difference exists between 1 and 2 and the minimum energy difference present between 4 and 5.