Who discovered atom first?

The concept of the atom was first introduced by the ancient Greek philosopher Democritus, but the scientific discovery of the atom was established by John Dalton in the early 19th century. The idea of atoms has a long history. Ancient philosophers and modern scientists both contributed to its discovery.

Early Ideas

• Democritus (460–370 BC): A Greek philosopher who first used the term “atomos” meaning indivisible. He proposed that all matter is made of small particles.

Modern Scientific Discovery

• John Dalton (1803): Proposed the Atomic Theory stating that matter is made of indivisible particles called atoms.
• He said atoms of the same element are identical, and atoms combine in simple ratios to form compounds.

Further Developments

• J.J. Thomson (1897): Discovered the electron, proving atoms are divisible.
• Ernest Rutherford (1911): Discovered the nucleus and proposed the nuclear model of the atom.
• Niels Bohr (1913): Suggested electrons move in fixed orbits around the nucleus.