Which feature was included in Thomson's model of the atom that was not present in Dalton's model?

• A. Electrons embedded within a positively charged sphere
• B. Orbiting electrons in fixed energy levels
• C. A nucleus containing protons and neutrons
• D. Atoms as indivisible solid spheres

Answer: (A)

Verified step by step guidance

1. Recall Dalton's atomic model, which described atoms as indivisible solid spheres without any internal structure or subatomic particles.
2. Understand that Thomson's model introduced the concept of internal structure within the atom, specifically the presence of negatively charged particles called electrons.
3. Recognize that Thomson proposed the 'plum pudding' model, where electrons are embedded within a positively charged sphere, balancing the overall charge of the atom.
4. Compare the features: Dalton's model had no electrons or internal charge distribution, while Thomson's model included electrons embedded in a positive sphere.
5. Conclude that the key new feature in Thomson's model, absent in Dalton's, is the presence of electrons embedded within a positively charged sphere.