From his experiments j. j. Thomson conclude that

J.J. Thomson's experiments with cathode ray tubes showed that all atoms contain tiny negatively charged subatomic particles or electrons. Thomson proposed the plum pudding model of the atom, which had negatively-charged electrons embedded within a positively-charged "soup."

J.J. Thomson could conclude that most of the mass of an atom is concentrated in its center, or the area where most of the parts of an atom such as the nucleus

Explanation:

the potential energy of the reactants is 200j.

from the energy diagram, the energy of the product formed is 350j; this means that, this reaction is an endothermic reaction, because it absorbs energy from its environment.