John Dalton’s atomic theory, proposed in the early 19th century, was groundbreaking at the time, but it also had some limitations and “throwbacks.” Here are five of the main throwbacks or shortcomings of Dalton’s atomic theory:

1. Indivisibility of Atoms:
   • Dalton’s theory initially proposed that atoms were indivisible and indestructible. This idea was later proven incorrect with the discovery of subatomic particles such as electrons, protons, and neutrons. Atoms can be divided into these subatomic particles, and they can also undergo nuclear reactions.
2. Lack of Isotopes:
   • Dalton’s theory did not account for the existence of isotopes. He believed that each element had a unique atomic mass. It was later discovered that some elements have multiple forms with different atomic masses (isotopes), which do not fit with Dalton’s original theory.
3. Inability to Explain Chemical Behavior:
   • While Dalton’s theory described the composition and structure of atoms, it couldn’t explain the chemical behavior and reactions of elements and compounds. It didn’t address the nature of chemical bonds, electron arrangements, or how atoms combine and interact to form molecules.
4. Assumption of Identical Atoms:
   • Dalton’s theory assumed that all atoms of a given element are identical. However, it’s now known that some elements can have different types of atoms with variations in the number of neutrons, leading to isotopes. This concept challenges the idea of identical atoms within the same element.
5. Lack of Subatomic Particles:
   • Dalton’s atomic theory did not account for the existence of subatomic particles, such as electrons, protons, and neutrons. It wasn’t until later scientific discoveries, particularly in the 20th century, that these subatomic particles were identified and their roles in atomic structure were understood.

While Dalton’s atomic theory was a significant step in the development of atomic science, it was later refined and expanded upon by other scientists, such as J.J. Thomson, Ernest Rutherford, Niels Bohr, and others, to account for the complexities of atomic and subatomic structure.