Question

5. Indicate the higher of the two energy states in each of the following pairs: a. 3d or 4s b. 4p or 5s c. 3d or 3p- d. 5s or 4f -5%

Answer 1

The energy level depends on the value of n+l where n is the principal quantum number and 'l' is the azimuthal quantum number. For same value of n+l, higher the value of n, higher is the energy level. The value of l is 0,1,2 and 3 for s, p, d and f respectively.

a)

Orbital	3d	4s
n	3	4
l	2	0
n+l	5	4

Thus, 3d is higher in energy because it has higher value of n+l

b)

Orbital	4p	5s
n	4	5
l	1	0
n+l	5	5

Here, the n+l values are equal. Hence, higher n has higher energy. Thus, 5s has higher energy level.

c)

Orbital	3d	3p
n	3	3
l	2	1
n+l	5	4

Thus, 3d is higher in energy because it has higher value of n+l

d)

Orbital	5s	4f
n	5	4
l	0	3
n+l	5	7

Thus, 4f is higher in energy because it has higher value of n+l