This question is about historical models of the atom.

Identify the names of the two historical atomic models shown as Model A and Model B in the diagram above.
Compare Model B with Model A. In your comparison, refer to the atomic structure, the distribution of electrical charge, and the location of mass in both models.
In 1932, the English physicist James Chadwick conducted experiments that led to the discovery of a previously unobserved subatomic particle.
Name the subatomic particle discovered by Chadwick.
Explain how discovering this particle resolved the mystery of isotopes, specifically focusing on how atoms of the same element can have different physical masses.