Atomic Theory Timeline by

Origine of The Atomic Theory (5th century BC)

veduvadie — 2024-07-08 17:10:58 UTC

The Atomic Theory was proposed by two Greek philosophers in the 5th century BCE, approximately 2500 years ago. Leucippus and Democritus suggested that matter is composed of small, indivisible particles called atoms. For exemple, gold is composed of gold particles, iron is composed of iron particles, cheese is composed of cheese particles, etc.

The Electrons (1897)

veduvadie — 2024-07-08 17:25:46 UTC

Trought an experiment using discharge tubes, J. J. Thompson proves that there are both negatively and positively charged components to matter.

These negatively charged particles are called electrons and have a mass approximately 1000 smaller than hydrogen. This is discovery was groundbreaking because, at the time, hydrogen was thought to be the smallest matter.

Plum Pudding Model (1904)

veduvadie — 2024-07-08 17:48:07 UTC

J. J. Thompson theorized that the negatively charged electrons were scattered randomly throughout a positively charged matrix. He compared his theory of the structure of an atome to a plum pudding.

The Nucleus (1909)

veduvadie — 2024-07-08 18:10:29 UTC

In 1909, Ernest Rutherford amade a major updated on our knowledge of the atome. Through methodical experiments using positively charged alpha particles shot at a thin piece of gold foil, he discovered the nucleus. He also concluded that atomes comprised of empty space.

The Proton (1917)

veduvadie — 2024-07-08 18:11:03 UTC

In 1917, the proton was discovered by Rutherford shortly after the discovery of the nucleus. Using similar methods, he not only discovered the proton but also discovered and provided a significant amont of information about the structure of the atome.

The Planetary Model (1911)

veduvadie — 2024-07-08 18:11:32 UTC

By analyzing the results of Rutherford's gold foil experiment, Niels Bohr was able to determine the most likely position of the electrons surrounding the nucleus. These calculations resulted in the creation of the Planetary model.

The Quantum Model (1927)

veduvadie — 2024-07-08 18:11:54 UTC

In 1927, Werner Heisenberg Mathematically determines that it is impossible to know the exact position and momentum of an electron. This means that we cannot conclude that electrons are aligne in circular orbits, thus the creation of the quantum model.