Given below are two statements :
Statement I : Bohr's theory accounts for the stability and line spectrum of Li⁺ ion.
Statement II : Bohr's theory was unable to explain the splitting of spectral lines in the presence of a magnetic field.
In the light of the above statements, choose the most appropriate answer from the options given below :

Solution

Chemistry ma’am · 4 steps

Before trusting Bohr for any ion, count its electrons: the model works only when there is exactly one.

1. Where Bohr works. Bohr's model treats one electron moving around a nucleus. It explains the stability and line spectrum only of one-electron species such as H, He⁺ and Li²⁺.
2. Statement I. Lithium has Z = 3, so Li⁺ has 3 - 1 = 2 electrons. With two electrons, the electron–electron repulsion is not part of Bohr's model, so it cannot account for the spectrum of Li⁺. Statement I is false.
3. Statement II. In a magnetic field, spectral lines split into several closely spaced lines. This is the Zeeman effect. Bohr's model has only one quantum number n for each orbit, so it cannot explain this splitting. Statement II is true.
4. So. Statement I is false and Statement II is true, which is option (a).

The idea to keep. Bohr's model is for one-electron species only: H, He⁺, Li²⁺, Be³⁺. It also fails for the Zeeman (magnetic) and Stark (electric) splitting of lines.

Answer from the NTA final answer key. Solution by PrepWiser.