Question
Energy and radius of first Bohr orbit of He ^ + and Li ^ 2+ are [Given R _ H =2.18 10^ -18 ~J , a _0=52.9 pm ]
NEET
Chemistry
Structure of Atom
2025
NEET 2025
NEET Chemistry Question (2025) — Solution
Options
- A. aligned & E _ n ( Li ^ 2+ )=-19.62 10^ -18 ~J ; \\ & r _ n ( Li ^ 2+ )=17.6 pm \\ & E _ n ( He ^ + )=-8.72 10^ -18 ~J ; \\ & r _ n ( He ^ + )=26.4 pm aligned
- B. aligned & E _ n ( Li ^ 2+ )=-8.72 10^ -18 ~J \\ & r _ n ( Li ^ 2+ )=26.4 pm \\ & E _ n ( He ^ + )=-19.62 10^ -18 ~J ; \\ & r _ n ( He ^ + )=17.6 pm aligned
- C. aligned & E _ n ( Li ^ 2+ )=-19.62 10^ -16 ~J \\ & r _ n ( Li ^ 2+ )=17.6 pm \\ & E _ n ( He ^ + )=-8.72 10^ -16 ~J \\ & r _ n ( He ^ + )=26.4 pm aligned
- D. aligned & E _ n ( Li ^ 2+ )=-8.72 10^ -16 ~J \\ & r _ n ( Li ^ 2+ )=17.6 pm \\ & E _ n ( He ^ + )=-19.62 10^ -16 ~J ; \\ & r _ n ( He ^ + )=17.6 pm aligned
Answer
A. aligned & E _ n ( Li ^ 2+ )=-19.62 10^ -18 ~J ; \\ & r _ n ( Li ^ 2+ )=17.6 pm \\ & E _ n ( He ^ + )=-8.72 10^ -18 ~J ; \\ & r _ n ( He ^ + )=26.4 pm aligned
Step-by-step solution
aligned & E_n=-2.18 10^ -18 Z^2 n^2 J \\ & For He ^ + E _1=-2.18 10^ -18 2^2 1^2 ~J \\ & =-8.72 10^ -18 ~J \\ & For Li ^ 2+ E _1=-2.18 10^ -18 3^2 1^2 ~J \\ & =-19.62 10^ -18 ~J \\ & r _ n =52.9 n ^2 Z pm \\ & For He ^ + r _1=52.9 1^2 2 pm =26.4 pm \\ & For Li ^ 2+ r _1=52.9 1^2 3 pm =17.6 pm aligned
Related: Chemistry — Structure of Atom · All PYQ Banks