Which One of the Following Is Not Part of Dalton’s Atomic Theory?


Jane Flores

John Dalton, an English chemist and physicist, proposed the atomic theory in the early 1800s. This theory revolutionized the way scientists viewed matter and its composition.

The atomic theory is based on several fundamental ideas, including the notion that all matter is composed of tiny particles called atoms. However, there are a few things that Dalton’s Atomic Theory does not include. In this article, we will explore these exceptions.

Dalton’s Atomic Theory

Before we dive into what Dalton’s Atomic Theory does not include, let’s take a quick look at the basic principles of his theory.

  • All matter is composed of tiny particles called atoms.
  • Atoms of one element are identical in size, mass, and other properties.
  • Atoms cannot be created, divided into smaller particles, or destroyed.
  • Atoms combine in fixed ratios to form compounds.
  • Chemical reactions involve the rearrangement of atoms.

What Is Not Included in Dalton’s Atomic Theory?

While John Dalton’s atomic theory laid down some solid foundations for understanding matter and its composition, it did not include everything we know about atoms today.

The Existence of Subatomic Particles

Dalton’s atomic theory proposed that atoms were indivisible and indestructible. However, scientists later discovered that atoms are made up of even smaller particles called protons, neutrons, and electrons. These subatomic particles have different properties such as charge and mass.

The Concept Of Isotopes

Dalton’s atomic theory did not take into account isotopes – atoms with the same number of protons but different numbers of neutrons. It was only later discovered that isotopes exist and play an essential role in nuclear chemistry.

The Existence of Radioactivity

Dalton’s atomic theory also did not include the concept of radioactivity. It was only later discovered that some elements are naturally radioactive, meaning that they emit radiation as they decay over time.


John Dalton’s Atomic Theory was a significant milestone in the development of modern chemistry. It laid down the foundation for our understanding of atoms and their behavior.

However, as science progressed, we discovered that there were a few things that Dalton’s Atomic Theory did not include, such as subatomic particles, isotopes, and radioactivity. Despite these limitations, Dalton’s Atomic Theory remains an essential contribution to our understanding of matter and its composition.