Final answer:
John Dalton's atomic theory, based on experiments and the laws of chemical combination, postulated that matter is composed of indivisible atoms, which combine in fixed ratios to form compounds. Despite its early acceptance, the theory was later updated with the discovery of subatomic particles and isotopes.
Step-by-step explanation:
Dalton's Atomic Theory and Model
John Dalton was an English scientist who greatly advanced our understanding of the atomic nature of matter. From his experiments and observations, as well as the work from his peers, he proposed what is now called Dalton's atomic theory. His model postulated several key points:
- All matter is made up of indivisible particles called atoms.
- Atoms of a specific element are identical in size, mass, and properties.
- Atoms cannot be created, divided, or destroyed.
- Atoms of different elements combine in simple, whole-number ratios to form chemical compounds.
- In chemical reactions, atoms are rearranged, but the way they are bound may change.
Dalton's model was a solid sphere structure, implying that atoms were the smallest indivisible units of matter. His discovery included insights into the Law of Conservation of Mass, Law of Constant Composition, and the Law of Multiple Proportions. These laws supported his atomic theory, especially observing that matter always combined in fixed ratios of weight and supported Proust's law of definite proportions. Despite its initial success, some parts of Dalton's atomic theory, such as atoms being indivisible or all atoms of an element being identical, are no longer considered valid due to the discovery of subatomic particles and isotopes.