Which two natural laws were successfully explained by Dalton's Atomic Theory?

Question

I have this question and:

Name two modifications that had to be made to the original Dalton's Atomic Theory to incorporate new experimental evidence and briefly discuss this evidence.

I know I learned it and wrote it down somewhere and I cannot for the life of me find it anywhere. These two questions are really starting to stress me out. Please HELP!!!

Answer 1

I know that originally Dalton's atomic theory said that atoms of the same element were identical. This is not the case: The discovery of the neutron has shown us that, in general, two elements of any given element can have different numbers of neutrons. (They must have the same numbers of protons, however.)

Dalton also said that it was not possible for atoms of one element to change into atoms of another element. The discovery of radioactivity and nuclear reactions, which can change atoms of one element into atoms of another element, invalidated this postulate.

Answer 2

he was right that atoms combine in whole number ratios and that chemical reactions occur when atoms are separated, joined, or rearranged and atoms of one element are never changed into atoms of another element