The modern atomic theory is a concept that revolutionized the way we understand matter and its composition. It was first proposed by John Dalton, an English chemist, in the early 19th century. His theory consisted of four statements that laid the foundation for modern atomic theory.

Dalton’s Atomic Theory

Statement 1: All matter is composed of atoms

Dalton’s first statement proposed that all matter is made up of tiny indivisible particles called atoms. These atoms are so small that they cannot be seen with the naked eye.

Statement 2: Atoms of the same element are identical

Dalton’s second statement suggested that all atoms of a particular element are identical in mass and properties. For example, all carbon atoms have the same mass and properties.

Statement 3: Atoms combine in whole number ratios

Dalton’s third statement stated that when atoms combine to form compounds, they do so in whole number ratios. This means that the ratio of one atom to another in a compound is always a small whole number.

Statement 4: Chemical reactions involve rearrangement of atoms

Dalton’s fourth and final statement proposed that chemical reactions involve only the rearrangement of atoms. In other words, during a chemical reaction, atoms are neither created nor destroyed; they simply rearrange themselves to form new compounds.


John Dalton’s atomic theory was a groundbreaking concept that provided us with a better understanding of matter and its composition. His four statements laid the foundation for modern atomic theory and helped us understand how elements combine to form compounds and how chemical reactions occur. Today, we continue to build on Dalton’s work as we explore even smaller particles such as protons, neutrons, and electrons in order to gain an even deeper understanding of the nature of matter.