What Are the Postulates of Dalton’s Atomic Theory?


Diego Sanchez

The foundation of modern chemistry was built on the work of John Dalton, who developed the atomic theory in the early 19th century. This theory revolutionized our understanding of matter and laid the groundwork for much of the scientific progress that followed.

Dalton’s atomic theory consists of several postulates that explain how atoms behave and interact with each other. In this article, we will explore those postulates in detail.

Postulate 1: Elements are made up of tiny particles called atoms.

The first postulate of Dalton’s atomic theory states that all elements are composed of small particles known as atoms. These atoms are indivisible and indestructible, meaning they cannot be broken down into smaller components by physical or chemical means. This idea was groundbreaking at the time, as scientists had previously believed that matter could be infinitely divided.

Postulate 2: Atoms of a given element are identical in size, mass, and other properties.

Dalton’s second postulate states that all atoms of a particular element are identical to each other in terms of size, mass, and other properties. For example, all carbon atoms have the same mass and size, regardless of whether they are found in a diamond or a pencil lead.

Postulate 3: Atoms cannot be created, destroyed or transformed into atoms of another element.

According to Dalton’s third postulate, atoms cannot be created or destroyed through ordinary chemical reactions. In addition, they cannot be transformed into atoms of another element. For example, if you burn wood, the resulting ash is still made up entirely of carbon atoms; none have been destroyed or transformed into oxygen or any other element.

Postulate 4: Compounds form when atoms combine in small whole-number ratios.

Dalton’s fourth postulate explains how compounds are formed from individual atoms. It states that atoms combine in small whole-number ratios to form compounds. For example, water is made up of two hydrogen atoms and one oxygen atom, which combine in a 2:1 ratio.


In summary, Dalton’s atomic theory consists of four postulates that explain the behavior and properties of atoms. These postulates have been foundational in our understanding of matter and continue to be relevant today. By understanding the basics of this theory, we can better appreciate the complexity and beauty of the world around us.