This was the first truly established scientific theory of the atom. He developed the law of multiple proportions and proposed a coherent scientific theory of the atom.Īccording to Dalton, atoms were indivisible and indestructible particles, each with unique characteristics. John Dalton, in the early 19th century, took atomic theory to a new height. Early 19th Century: John Dalton and the First Atomic Theory The Law of Conservation of Mass (1789) stated that the total mass in a chemical reaction remains constant, while the Law of Definite Proportions (1799) stated that the masses of the constituent compounds will always have the same proportions.Īlthough these laws laid the foundation, the notion of atomic theory had not yet been named. 18th Century: Fundamental Chemical Lawsĭuring the 18th century, Antoine Lavoisier and Joseph Louis Proust formulated fundamental laws in chemistry. These atoms were considered the fundamental and indivisible units of reality, laying the foundations of atomic theory. In ancient Greece, thinkers such as Leucippus and Democritus proposed the revolutionary idea that matter is composed of indivisible particles called atoms.

From early philosophical speculations to modern quantum models, each stage has contributed to our understanding of the intimate nature of reality.īelow we present a timeline of the most important scientific advances and discoveries related to atomic theory: Ancient Greece: the Philosophical Seeds (5th Century BC) History and Timeline of Atomic TheoryĪtomic theory has undergone a fascinating evolution over the centuries. The theory of the atom provides a model for understanding the structure and behavior of atoms, as well as their interactions in chemical reactions. It proposes that matter is composed of basic units called atoms, which are the smallest and indivisible units of a chemical element. Definition: What Is Atomic Theory?Ītomic theory is a conceptual framework that describes the fundamental nature of matter at the smallest level. Atomic theory has been the backbone of modern chemistry and physics, an idea that has evolved over the centuries and revolutionized our understanding of the world around us.įrom the earliest speculations of Greek philosophers to sophisticated contemporary quantum theories, atomic theory has undergone a fascinating evolution that has transformed humanity's understanding of matter and energy.

What is the atomic theory