The Bohr radius of a hydrogen like species is 70.53 pm. The species and the stationary state (n) are respectively (Given : Hydrogen atom Bohr radius is 52.9 pm)
- Li2+, 3
- He+, 3
- He+, 2
- Li2+, 2
Answer
(4) Li2+, 2
Solution
For a hydrogen-like species: rn = 52.9 n2Z pm
⇒ n2Z = 70.5352.9 = 1.333 = 43
⇒ n2 = 4 and Z = 3 ⇒ n = 2, Z = 3
∴ The species is Li2+ (Z = 3) in the stationary state n = 2.
(Check: He+, n = 3 gives 52.9 92 = 238 pm; Li2+, n = 3 gives 158.7 pm.)
Answer: (4)