Final answer:
Atoms are not indestructible and indivisible; they can be broken down into subatomic particles, and they can be created or destroyed through nuclear reactions. Moreover, atoms of the same element can have different masses (isotopes), and atoms of different elements can sometimes have the same mass.
Step-by-step explanation:
The postulate of Dalton's atomic theory that is not accurate is that atoms are tiny, indivisible, and indestructible. Over time, scientific evidence has revealed that atoms can indeed be divided into smaller particles, such as protons, neutrons, and electrons.
Moreover, with techniques such as nuclear fission and fusion, the transmutation of one atom into another can occur—meaning atoms can be created and destroyed in a certain sense. Additionally, Dalton believed that atoms of the same element were identical in mass which was later found to be untrue with the discovery of isotopes, where atoms of the same element can have different masses, as is the case with chlorine's isotopes. On the other hand, atoms of different elements can have the same atomic mass, an example being argon and calcium, both with an atomic mass of 40 amu, which refutes the postulate that atoms of different elements can have the same ultimate particle mass.