Question

In which of the following option, energy value is given in correct order ?

• A. $ns<np<nd<(n-1)f$
• B. $ns<np<(n-1)d<(n-2)f$
• C. $ns<np<(n-1)d<(n-1)f$
• D. $ns<(n-1)d<np<(n-1)f$

Answer 1

Answer: (D)

$ns<(n-1)d<np<(n-1)f$

We use $n+l$ rule for calculating energies

value of l varies:

s = 0

p = 1

d = 2

f = 3

so ns have energy n + 0 = n

(n-1)d have energy n -1 + 1 = n

np have energy n + 1

(n-1)f have energy n -1 + 2 = n + 1

if two shells have same value then we consider energy in given order

$s>p>d>f$

we get: $ns<(n-1)d<np<(n-1)f$