Dalton’s Atomic Theory of Matter
About 2 min read
(updated 8 February 2022)
The atomic theory of matter states that matter is composed of discrete units called atoms. This theory was first suggested in ancient Greece and was later theorized by chemist John Dalton in 1808. Although Dalton’s theory remains valid, it also includes some misconceptions.
Modern atomic theory goes beyond Dalton’s views and includes concepts such as subatomic particles and isotopes.
Questions you may have include:
- What was the background of Dalton’s theory?
- What are Dalton’s rules and corrections needed?
- What are some issues in modern atomic theories?
This lesson will answer those questions. Useful tool: Units Conversion
Background of theory
It began as a philosophical concept in ancient Greece and entered the scientific mainstream in the early 19th century when discoveries in the field of chemistry showed that matter did indeed behave as if it were made up of atoms.
John Dalton, a British school teacher, published his theory about atoms in 1808. His findings were based on experiments and the laws of chemical combination.
Basic rules
Basic rules of the theory—along with corrections to those rules—include:
Matter made of atoms
All matter is made of atoms, which are indivisible and indestructible.
Although all matter is made up of atoms, it was later found that atoms can be divided and even destroyed.
Atoms of element identical
All atoms of a given element are identical in mass and properties.
However, there are variations of atoms, called isotopes.
Compounds formed by combination of atoms
Compounds are formed by a combination of two or more different kinds of atoms.
But also two or more atoms of the same element can form molecules, although they are not called compounds.
Rearrangement of atoms
A chemical reaction is a rearrangement of atoms.
Actually, in chemical reactions, atoms can be combined, separated, or rearranged.
Modern ideas
Dalton’s atomic theory was a good start. However, there have since been modern theories concerning the nature of matter and atoms.
Brownian Motion
Brownian motion showed atoms and molecules in motion.
Subatomic particles and of the nucleus
The atom was found to consist of a nucleus and subatomic particles.
Isotopes
An element can have more or less neutrons in its nucleus.
Physical model of the atom
The model of the atom included the Bohr Model of a nucleus surrounded by electrons in orbit and Quantum Theory, where particles can exist as waves.
(See Structure of the Atom for more information.)
Summary
The atomic theory of matter states that matter is composed of discrete units called atoms was created by chemist John Dalton in 1808. Although Dalton’s theory remains valid, it also includes some misconceptions. Modern atomic theory goes beyond Dalton’s views and includes concepts such as subatomic particles and isotopes.
Have an atomic view of things
Resources and references
Websites
John Dalton – Wikipedia
Postulates of Dalton’s Atomic Theory – LibreTexts.org
Atomic Theory – Wikipedia