2.16 (i) The energy associated with the first orbit in the hydrogen atom is
–2.18 × 10
–18 J atom–1. What is the energy associated with the fifth orbit?

(ii) Calculate the radius of Bohr’s fifth orbit for hydrogen atom.


(i)Energy associated with the fifth orbit of hydrogen atom is calculated as:

E5 = -2.18 x 10-1852 = -2.18 x 10-1825
E5 = 8.72 × 10-20 J 

(ii) Radius of Bohr’s n
th orbit for hydrogen atom is given by, rn = (0.0529 nm) n2
For, n = 5
r5 = (0.0529 nm) (5)2
r5 = 1.3225 nm