What is one limitation of Dalton's atomic theory?

One limitation of Dalton's atomic theory is its failure to account for isotopes. Dalton proposed that all atoms of a given element are identical in mass and properties. However, this statement does not hold true for elements with isotopes, which are variants that have the same number of protons but different numbers of neutrons, leading to variations in mass. The existence of isotopes demonstrates that there can be variations within a single element, contradicting Dalton's original assertion of uniformity among atoms of the same element. This limitation underscores the need for a more refined understanding of atomic structure that accommodates the diversity of isotopic forms.