Question

Which of the following statements is inconsistent with the Bohr model of the atom? A. Energy levels of the electron are stable and discrete. B. An electron emits or absorbs radiation only when making a transition from one energy level to another. C. To jump from a lower energy to a higher energy orbit, an electron must absorb a photon of precisely the right frequency such that the photon's energy equals the energy difference between the two orbit D. To jump from a higher energy to a lower energy orbit, an electron absorbs a photon of a frequency such that the photon's energy is exactly the energy difference between the two orbits.

Short answer

D: An electron emits, not absorbs, a photon when jumping to a lower energy level.

Step-by-step solution

Understanding Stable and Discrete Energy Levels

The Bohr model states that electrons orbit the nucleus in specific, stable, and discrete energy levels. Statement A is consistent with the Bohr model.

Emission and Absorption of Radiation

The Bohr model posits that electrons can only emit or absorb radiation when they transition from one energy level to another. This means that statement B is also consistent with the Bohr model.

Photon Absorption in Energy Transition

According to the Bohr model, for an electron to jump from a lower energy level to a higher one, it must absorb a photon whose energy equals the difference between these levels. Statement C aligns with this rule.

Photon Emission in Energy Transition

The Bohr model explains that to transition from a higher energy level to a lower one, an electron emits a photon whose energy equals the difference between these levels. However, statement D incorrectly states that the electron absorbs a photon in this process, which is not consistent with the Bohr model.

Key concepts

Energy Levels

In the Bohr model of the atom, energy levels are specific and stable orbits in which electrons reside. Each of these orbits corresponds to a different energy state. Think of these energy levels as steps on a ladder: each step represents a stable, discrete orbit where an electron can be found.
Importantly, these energy levels are quantized. This means that electrons can only exist in particular orbits with fixed energies and cannot reside between them.
The energy of each level is negative and increases (gets less negative) as you move farther from the nucleus. Therefore, electrons in lower energy levels are more tightly bound to the nucleus than those in higher levels. The quantization of energy levels is a fundamental aspect of the Bohr model and helps explain why atoms absorb and emit light at specific wavelengths.

Electron Transitions

Electron transitions refer to the movement of electrons between energy levels in an atom. In the Bohr model, these transitions are strictly between fixed orbits.
When an electron transitions from one energy level to another, it must either absorb or emit a specific amount of energy corresponding to the difference between the initial and final levels.
There are two types of transitions:

• Excitation: When an electron moves from a lower energy level to a higher one by absorbing energy.
• Relaxation: When an electron moves from a higher energy level to a lower one by emitting energy.

These transitions explain the discrete spectral lines observed in atomic spectra, as each line corresponds to a specific electron transition.

Photon Absorption

Photon absorption occurs when an electron absorbs a photon and moves to a higher energy level. In the Bohr model, this process requires the photon to have an exact amount of energy equal to the difference between the two energy levels.
For example, if an electron in an atom is in the first energy level and needs to jump to the second energy level, it has to absorb a photon with energy equal to the energy gap between these two levels.
This is crucial because if the photon's energy is not exactly equal to the energy difference, the electron cannot absorb it and will remain in its initial state.
This principle explains why atoms absorb light at certain wavelengths, corresponding to the energy differences between their various energy levels.

Photon Emission

Photon emission is the process where an electron releases energy in the form of a photon and falls to a lower energy level. According to the Bohr model, the energy of the emitted photon equals the energy difference between the two energy levels involved in the transition.
For instance, if an electron moves from the second energy level to the first, it will emit a photon whose energy matches the gap between these two levels.
This emission process is responsible for the bright lines seen in the emission spectra of elements, as each line represents a photon emitted during an electron's downward transition.
It is essential to understand that during photon emission, energy is released, which is why this process often occurs spontaneously, especially when electrons are in excited states and seek to return to lower, more stable energy levels.