What Are 5 Postulates of Dalton’s Atomic Theory?


Jane Flores

Dalton’s Atomic Theory, proposed by John Dalton in 1808, was a significant milestone in the development of modern chemistry. This theory revolutionized the way we understand the composition and behavior of matter.

According to Dalton’s Atomic Theory, all matter is made up of tiny particles called atoms that are indivisible and indestructible. Let’s take a closer look at the 5 postulates of Dalton’s Atomic Theory:

Postulate 1: Elements are composed of small, indivisible particles called atoms

Dalton’s first postulate stated that all elements are composed of small particles called atoms that cannot be divided further. He believed that these atoms were the building blocks of matter and were responsible for all chemical reactions.

Postulate 2: Atoms of the same element have identical properties

Dalton’s second postulate stated that all atoms of a particular element are identical to each other in terms of their size, shape, mass, and chemical properties. This means that all carbon atoms have the same properties as each other, as do all oxygen atoms.

Postulate 3: Atoms can combine to form compounds

According to Dalton’s third postulate, atoms can combine with each other in fixed ratios to form compounds. For example, water is made up of two hydrogen atoms and one oxygen atom (H2O). Dalton believed that these ratios were always constant for a given compound.

Postulate 4: Chemical reactions involve the rearrangement of atoms

Dalton’s fourth postulate stated that chemical reactions involve the rearrangement of atoms from one molecule to another. He believed that during a chemical reaction, no new atoms were created or destroyed; they simply rearranged themselves into new molecules.

Postulate 5: Atoms cannot be created or destroyed

Finally, Dalton’s fifth postulate stated that atoms cannot be created or destroyed in a chemical reaction. This means that the total number of atoms before and after a reaction is always the same.


In conclusion, Dalton’s Atomic Theory was a groundbreaking concept that laid the foundation for modern chemistry. His five postulates provided a framework for understanding the behavior of matter at the atomic level. Although some of his ideas have been modified or disproven by modern science, his legacy lives on in our understanding of the fundamental building blocks of matter.