One key way Dalton’s atomic theory has been shown to be incorrect is his assertion that atoms are indivisible particles. The discovery of subatomic particles—protons, neutrons, and electrons—proved that atoms can be further subdivided, contradicting Dalton’s idea that atoms are the smallest indivisible units of matter
. Additionally, Dalton claimed that all atoms of a given element are identical in mass and properties. This has been disproven by the discovery of isotopes, which are atoms of the same element that have different masses due to varying numbers of neutrons. For example, chlorine has isotopes with mass numbers 35 and 37
. In summary, Dalton’s theory was incorrect in stating that atoms are indivisible and that all atoms of an element are identical in mass. These findings have been fundamental in advancing atomic theory beyond Dalton’s original postulates.
