How did John Dalton’s atomic theory explain chemical reactions?

John Dalton’s atomic theory, proposed in the early 19th century, provided a foundational explanation for chemical reactions by positing that matter is composed of small, indivisible particles called atoms.12

Dalton explained chemical reactions as the process of rearranging these atoms to form new substances. His model established several key principles:1

• Indestructibility: Atoms cannot be created, destroyed, or transformed into atoms of other elements during a reaction, which provided a theoretical basis for the law of conservation of mass.12
• Fixed Characteristics: Each element is characterized by the unique mass of its atoms, and all atoms of a specific element are identical in mass, size, and shape.32
• Whole-Number Ratios: When atoms combine to form molecules or compounds, they do so in small, whole-number ratios. This concept helped explain the law of definite proportions and the law of multiple proportions, where elements combine in predictable, consistent weights.24

By viewing reactions as the reorganization of these discrete, constant particles, Dalton transformed chemistry into a quantitative science.12