The results that demonstrated that elements combine in specific proportions because they are made of individual atoms were primarily due to the work of John Dalton, an English chemist and physicist, in the early 19th century.

Dalton's Atomic Theory, based on his observations and experiments, proposed the following:

* Elements are composed of tiny, indivisible particles called atoms.

* Atoms of the same element are identical in mass and properties.

* Atoms of different elements have different masses and properties.

* Chemical reactions involve the rearrangement of atoms, not their creation or destruction.

Dalton's Law of Multiple Proportions further solidified this concept. This law states that when two elements form more than one compound, the masses of one element that combine with a fixed mass of the other element are in ratios of small whole numbers. For example, carbon and oxygen can form two compounds: carbon monoxide (CO) and carbon dioxide (CO₂). The ratio of oxygen atoms in CO to CO₂ is 1:2, which aligns with Dalton's theory of atoms combining in specific proportions.

Other key contributors to the development of atomic theory include:

* Joseph Proust: His Law of Definite Proportions stated that a given chemical compound always contains the same elements in the same proportion by mass.

* Antoine Lavoisier: His work on conservation of mass helped lay the foundation for Dalton's atomic theory.

While Dalton's atomic theory has been modified over time with the discovery of subatomic particles and isotopes, it remains a fundamental cornerstone of modern chemistry, providing a framework for understanding the nature of matter and chemical reactions.