Which Statements in Dalton’s Atomic Theory Are Now Considered to Be Incorrect?


Diego Sanchez

Dalton’s Atomic Theory is considered to be a milestone in the history of science. It was proposed in the early 19th century and provided a foundation for modern atomic theory.

Although it was a groundbreaking theory, it is not entirely correct. In this article, we will explore which statements in Dalton’s Atomic Theory are considered incorrect.

What is Dalton’s Atomic Theory?

John Dalton was an English chemist who proposed the Atomic Theory in 1803. According to his theory, all matter is made up of tiny particles called atoms.

These atoms are indivisible and indestructible. He also proposed that all atoms of a given element are identical in mass and properties.

Which Statements Are Considered Incorrect?

1. Atoms Are Indivisible

Dalton believed that atoms were indivisible, but this statement is not entirely true. Atoms can be divided into subatomic particles like protons, neutrons, and electrons through various experiments such as the cathode ray experiment and the gold foil experiment.

2. All Atoms of an Element are Identical in Mass and Properties

This statement is also not entirely correct. Although most atoms of an element have the same number of protons (which determines their atomic number), they can have different numbers of neutrons (which determines their isotopes). Isotopes have different masses but similar chemical properties.

3. Chemical Reactions Involve the Rearrangement of Atoms

Dalton’s theory suggested that chemical reactions involve only the rearrangement of atoms between molecules without changing their identity or properties. However, modern atomic theory shows that chemical reactions involve breaking and forming bonds between atoms resulting in new molecules with different properties than the original ones.

4. All Matter is Composed of Atoms

This statement is generally true; however, there are a few exceptions. For example, subatomic particles like electrons and quarks are not considered atoms but are still considered matter.


Dalton’s Atomic Theory provided a foundation for modern atomic theory; however, it is not entirely correct. The theory’s limitations were overcome by subsequent discoveries in science that led to the development of modern atomic theory. Despite its incorrect statements, Dalton’s Atomic Theory remains an essential milestone in the history of science and continues to inspire further scientific advancements.