Final answer:
Dalton's Atomic Theory was refined to include the concept of isotopes, different ratios of atom combinations in compounds, and the discovery of electrons.
Step-by-step explanation:
Dalton's Atomic Theory was refined and added to over time, incorporating new information and understanding. One of the key additions to Dalton's theory was the concept of isotopes, which acknowledged that atoms of the same element could have different masses due to varying numbers of neutrons. Another refinement was the realization that atoms could combine in different ratios to form compounds, challenging the original idea of atoms always combining in fixed whole number ratios. Additionally, the discovery of the electron and its role in atomic structure further expanded and refined Dalton's theory.
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