J.J. Thomson's model for atom was proposed in 1904.
According to Thomson Atomic Model
- Positively Charged Sphere: Thomson envisioned the atom as a positively charged sphere of uniform density, like a giant ball of positive electricity.
- Embedded Electrons: He proposed that negatively charged electrons, particles he discovered in 1897, were scattered throughout this positive sphere, much like raisins in a plum pudding (hence the nickname).
- Overall Neutral: The number of positive and negative charges were equal, making the entire atom electrically neutral.
Achievements of Thomson's Atomic Model
Thomson model had very limited applications. It managed to explain the electron neutrality of the atom. It explained that total positive charge in the atom is equal to total negative charge in it. Hence, the atom is electronically neutral.
Limitations of Thomson's Atomic Model:
1. Mass Distribution: A major drawback was the assumption of even mass distribution. This clashed with later experiments suggesting most of the mass is concentrated in a tiny central core.
2. Static Electrons: The model didn't account for electron movement. Electrons were seen as fixed in place, which couldn't explain certain atomic behaviors.
Thomson's model, while ultimately superseded by Rutherford's nuclear model, was a crucial step. It introduced the concept of a subatomic particle (the electron) and laid the foundation for further exploration of atomic structure.
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