Question

look at the following image. what feature from this model caused scientists to develop a new theory about an atoms structure?
negative electrons float in a \soup\ of positively charged material.
positively charged particles can be ejected from an atom.
there is a soup where only negative particles are free to move.
electrons form the cloud that positive charged particle move freely in.

Explanation:

The image represents Thomson's plum - pudding model of the atom. In this model, negative electrons float in a "soup" of positively charged material. Rutherford's gold - foil experiment (which led to a new atomic theory - the nuclear model) was in part a response to challenges with the plum - pudding model. The plum - pudding model's structure (negative electrons in a positive "soup") was what was being re - evaluated. The other options either mis - represent the plum - pudding model (e.g., “positively charged particles can be ejected from an atom” is not a key feature of this model in the context of prompting a new theory, “there is a soup where only negative particles are free to move” is incorrect as the positive “soup” is also a feature, “electrons form the cloud that positive charged particle move freely in” is the opposite of the plum - pudding model)

Answer:

Negative electrons float in a "soup" of positively charged material.