Final answer:
John Dalton introduced atomic theory, proposing that matter is composed of indivisible atoms, and laid out principles that describe chemical behavior. His Law of multiple proportions explains the fixed ratios in which elements combine, illustrated by different compounds formed from carbon and oxygen. Dalton's foundational work was later modified to incorporate discoveries of subatomic particles and isotopes.
Step-by-step explanation:
John Dalton's Atomic Theory
John Dalton was a pivotal figure in the development of atomic theory. His theory gave birth to the modern understanding of matter and its composition at the atomic level. Dalton proposed that matter is composed of small, indivisible particles called atoms. He formulated several principles including the ideas that elements are made of identical atoms, atoms of different elements differ, atoms of elements combine in fixed ratios to form compounds, and that chemical reactions involve the reorganization of atoms.
One of the key aspects of Dalton's theory was the Law of multiple proportions, which explains how elements can combine in different ratios to form different compounds. An example of this is carbon and oxygen forming both carbon monoxide (CO) and carbon dioxide (CO2), with the ratio of oxygen to carbon being different in each compound.
Dalton's ideas were later modified by other scientists, as they discovered the subatomic structure of atoms and the existence of isotopes, which showed that atoms could be divided into smaller parts and that atoms of the same element can have different masses. Despite these modifications, Dalton's work remains foundational in the field of chemistry.