Question

Consider an atom of Li2+ which is a unielectron syestem and hence bhor's model is applicable to it.
If R° is the radius of first orbit in H atom. What is the radius of e- in second excited state in Li2+?

Answer 1

We are required to find the energy required to excite doubly ionized lithium. We know that,

En = –13.6 Z2 / n2

Hence, the excitation energy = ΔE = E3 – E1 = –13.6 × (3)2 [1/32 – 1/12]

= +13.6 × (9) [1–1/9] = 13.6 × (9) (8/9) = 108.8 eV.

Wavelength λ = hc / ΔE = (6.63 × 10–34) (3×108) / (13.6 × 8) (1.6 × 10–19)

= (6.63 × (3) / (13.6) (8)(1.16)) 10–7

= 114.26 × 10–10 m

= 1143 A

(ii) From the excited state (E3), coming back to ground state, there can be 3C2 = 3 possible radiations