What part of dalton’s atomic theory is disproved by the existence of isotopes?

The part that says all atoms of a specific element always have the same mass. Isotopes of an atom have varying masses compared to the standard version of the element.

Ifound this on google “these two compounds have a different ionic structure. caesium ion is larger in size when compared to the sodium ion. the charge gets more area to spread out evenly. so caesium chloride has a lower melting point than sodium chloride.” i hope this you for what your looking for

Wow that a lot of text for my tiny so i no wanna answer