Final answer:
John Dalton's atomic model believed in indivisible particles, while Niels Bohr proposed electrons in specific energy orbits or shells around the nucleus. The change from Dalton to Bohr's model was due to advancements in scientific knowledge and experimental evidence. Both models believed in fixed orbits, but Bohr's model was more accurate.
Step-by-step explanation:
John Dalton and Niels Bohr had different models of the atom and proposed their theories for different reasons. John Dalton believed that atoms were indivisible particles, while Niels Bohr proposed the existence of a nucleus and electron shells. Dalton's model was further developed by others to include electrons within the nucleus, but Bohr expanded on this by introducing the idea of electrons in specific energy levels or orbits around the nucleus.
The change in the atomic model from Dalton to Bohr was mainly due to advancements in scientific knowledge and experimental evidence. Rutherford's experiments provided evidence for the existence of the atomic nucleus, which led to Bohr's proposal of electron orbits. Additionally, studies on the emission spectra of hydrogen helped Bohr develop his model further.
It is important to note that both Dalton and Bohr believed in the existence of electrons in fixed orbits, but Bohr's model was more refined and accurate in explaining the behavior of electrons within an atom. Dalton also suggested that electrons are continuously moving, while Bohr proposed the idea of stationary orbits at specific distances from the nucleus.