Question

how is energy gap between (n-2)f and (n-1)d is large??​

Answer 1

Answer:

The gap between the first two energy levels, n1 and n2, is the largest because these two values have the largest difference between the excited and ground state. For example, a drop from n2 to n1 has ALOT more energy than a drop from n4 to n1. Energy levels are also closer together as you move up, from 1 to 7.