Compare all the proposed models of an atom given in this chapter.

The comparison of the proposed atomic models—Thomson’s model, Rutherford’s model, and Bohr’s model—in a way suitable for understanding:

Thomson’s Model (Plum Pudding Model):
– Structure: Described an atom as a positively charged sphere with embedded electrons, resembling plums in a pudding.
– Key Points: Lacked a central nucleus and didn’t explain atomic stability or spectral lines.
– Limitations: Couldn’t account for the structure’s stability or the specific spectral lines emitted by different elements.

Rutherford’s Model (Nuclear Model):
– Structure: Proposed a central, positively charged nucleus surrounded by orbiting electrons.
– Key Points: Failed to explain the stability of electrons in orbits or the discrete spectral lines observed in atomic spectra.
– Limitations: Couldn’t address why electrons didn’t spiral into the nucleus due to electromagnetic radiation emission as per classical physics.

Bohr’s Model:
– Structure: Retained the central nucleus but introduced the concept of quantized electron orbits or energy levels.
– Key Aspects: Introduced the idea of fixed energy levels for electrons, explaining discrete spectral lines observed in atomic spectra.
– Successes: Successfully explained hydrogen’s spectral lines and introduced quantization of angular momentum.

Comparison:
1. Nucleus: Thomson lacked a defined nucleus; Rutherford and Bohr introduced a central nucleus.
2. Electron Orbits: Thomson lacked defined orbits; Rutherford proposed planetary-like orbits; Bohr introduced quantized orbits.
3. Stability: Thomson and Rutherford couldn’t explain electron stability; Bohr introduced stable, quantized orbits.
4. Spectral Lines: Only Bohr’s model explained discrete spectral lines observed in atomic spectra.
5. Quantization: Bohr’s model introduced quantization of energy levels and angular momentum, a step toward understanding quantum principles.

Overall, while each model contributed to our understanding of the atom, Bohr’s model made strides by introducing quantized orbits and explaining spectral lines. However, advancements in quantum mechanics surpassed these models, providing a more comprehensive understanding of atomic structure and behavior.