Which of Dalton’s Atomic Theory Is Wrong?


Vincent White

John Dalton, a British chemist and physicist, introduced the Atomic Theory in 1808. His theory revolutionized our understanding of the physical world by proposing that all matter is made up of tiny, indivisible particles called atoms.

However, as our knowledge and techniques have advanced, some of Dalton’s postulates have been proven to be incorrect. In this article, we will explore which parts of Dalton’s Atomic Theory are wrong.

Postulate #1: All Matter Is Made Up Of Atoms

Dalton’s first postulate states that all matter is made up of atoms. This concept was groundbreaking at the time and has been proven true by various experiments over time. However, recent discoveries have shown that subatomic particles such as protons, neutrons, and electrons are present within atoms.

Conclusion: Although this postulate is not entirely accurate in its original form, it does hold true for the most part.

Postulate #2: Atoms Are Indivisible

Dalton’s second postulate stated that atoms were indivisible and cannot be broken down into smaller particles. However, in the early 20th century, experiments involving radioactivity showed that atoms can indeed break down into smaller particles.

Conclusion: This postulate is incorrect as atoms can undergo nuclear decay and transform into smaller particles.

Postulate #3: All Atoms Of An Element Are Identical

According to Dalton’s third postulate, all atoms of an element are identical in mass and other properties. However, with advancements in technology and experimentation methods such as mass spectrometry, it has been discovered that isotopes exist – atoms of an element with different numbers of neutrons resulting in different masses.

Conclusion: This postulate is incorrect as isotopes reveal differences between individual atoms of an element.

Postulate #4: Chemical Reactions Involve The Rearrangement Of Atoms

Dalton’s fourth postulate states that chemical reactions involve the rearrangement of atoms, and no atoms are created or destroyed in a chemical reaction. While this is true for the most part, there are situations where atoms can be created or destroyed during a reaction. For example, nuclear reactions can create or destroy atoms.

Conclusion: This postulate is mostly correct but not entirely accurate in all situations.


John Dalton’s Atomic Theory was a significant contribution to the scientific community and laid the foundation for modern atomic theory. However, with advancements in technology and experimentation methods, some of his postulates have been proven incorrect. Nevertheless, his ideas remain relevant today and continue to inspire scientific research and discovery.

In summary, Dalton’s second and third postulates are incorrect while his first and fourth postulates are partially correct but not entirely accurate in all scenarios.