Which parts of John Dalton's atomic theory were later shown to be incorrect?

While John Dalton’s atomic theory was foundational to modern chemistry, several of his original postulates were later proven incorrect by subsequent scientific discoveries:

• Indivisibility of Atoms: Dalton proposed that atoms were indestructible and could not be divided into smaller pieces. We now know that atoms are composed of subatomic particles, including electrons, protons, and neutrons.12
• Identical Mass: Dalton stated that all atoms of a specific element are identical in mass. The discovery of isotopes—atoms of the same element with different numbers of neutrons and thus different masses—disproved this assumption.13
• Immutability: Dalton believed atoms could not be transformed into atoms of other elements. This was overturned by the discovery of radioactivity, which demonstrated that atoms can transmute into different elements through processes like alpha decay and beta decay.124
• Interatomic Forces: Dalton’s belief that only like atoms repel one another was also found to be erroneous, though it served as a useful early model for understanding gas mixtures.5