Question

Which of the following can be explained by the Bohr model?
${\text{A}}{\text{.}}$ The spectrum of hydrogen atom only
${\text{B}}{\text{.}}$ Spectrum of an atom or ion containing only one electron
${\text{C}}{\text{.}}$ The spectrum of hydrogen molecules
${\text{D}}{\text{.}}$ Solar spectrum

Answer 1

Hint- Here, we will proceed by mentioning important postulates of the Bohr model and then, we will discuss the validity of Bohr’s model for multi-electron atoms along with the reason for its non-validity.

Complete answer:
Some of the Bohr model’s postulates are mentioned under.
${\text{1}}{\text{.}}$ Electrons in an atom revolve around the positively charged nucleus in a definite circular path called as shells or orbits.
${\text{2}}{\text{.}}$ Each orbit or shell has a fixed energy which is known as orbital shells.
$3.$ The energy level is an integer (n = 1, 2, 3, ...) known as the quantum number. This set of quantum numbers starts with n=1 having the lowest energy level from the nucleus side. The n=1, 2, 3, 4 ... orbits are numbered as K, L, M , N .... Shells and when an electron reaches the lowest level of energy it is assumed to be in ground condition.
$4.$ The electrons in an atom travel from a lower energy level to a higher energy level by acquiring the energy needed, and by losing energy, an electron moves from a higher energy level to a lower energy level.
The biggest problem with Bohr 's model is that it fits very well with multi-electron atoms that have only one electron, like H but not at all. Bohr has been able to predict the energy difference between each energy level , allowing us to predict the energies of each line in the hydrogen emission spectrum, and understand why electron energies are quantized.
When applied to the multi-electron atoms, the Bohr model breaks down. It doesn't take into account sublevels (s, p, d, f), orbitals or electron spins. The Bohr model allows an electron's classical behavior (orbiting the nucleus at discrete distances from the nucleus.
Therefore, the Bohr model can explain the spectrum of an atom or ion containing only one electron.

Hence, option B is correct.

Note- Bohr model does not describe the Zeeman Effect when the spectral line is split into multiple components in the presence of a magnetic field. This is in violation of the Heisenberg theory of ambiguity. The Bohr model assumes that electrons have both a known radius and an orbit which Heisenberg claims is unlikely.