Atom Model Timeline by Maggie Lin

Ancient Greece/India 400s BC

mlin30_4 — 2025-02-11 15:46:11 UTC

Many people were part of the discovery of atoms, but the idea was mainly credited to Democritus and his teacher Leucippus. They named the discovery after the word indivisible in Greek. Though their idea of the atom is very different from the modern day example, some aspects of their analysis are still valid till this day. They firmly believed that everything was made of atoms and that atoms are invisible and indivisible.

1803

mlin30_4 — 2025-02-11 15:50:01 UTC

English Chemist, John Dalton gave the original ancient Greek idea of atoms a more scientific twist. He described atoms as small, firm spheres. He also came up with the first symbols for elements.

Late 1800s

mlin30_4 — 2025-02-11 18:21:52 UTC

Joseph John Thompson or (JJ) made a discovery that contradicted many past ideas. JJ discovered that atoms are divisible, he came across this conclusion because of an experiment he did on cathode rays. During the same experiment JJ also discovered the electron, which he referred to as the corpuscle. In 1904, JJ developed the plum pudding model of the atom. This model is a positively charged sphere.These series of advancements won him the Nobel Prize in 1906.

Earnest Rutherford 1911

mlin30_4 — 2025-02-12 16:10:30 UTC

New Zealand Physicist, Earnest Rutherford, who is also a student under JJ. Rutherford experimented with firing positive charged alpha particles against gold foil. He was trying to prove that JJ's model of an atom was correct, instead he did the opposite. Through this experiment, Rutherford concluded that positively charged particles only reside in the center of the atom, or the nucleus. Opposed to JJ's idea that the whole atom is positively charged. Rutherford also made a atom model of his own, the nuclear model.

Niels Bohr 1913

mlin30_4 — 2025-02-12 16:24:18 UTC

Danish Physicist, Niels Bohr noticed many flaws to Rutherford's atom design. Bohr's suggestion uses quantum theory to explain the energy levels of electrons. Unfortunately, his model only worked for hydrogen atoms.

1926

mlin30_4 — 2025-02-12 16:33:56 UTC

Austrian Physicist, Erwin Schrodinger proposed that electrons moves like waves. Schrodinger approached developing an atomic model with mathematical equations. His conclusion shows that the atom is a nucleus surrounded by clouds of electrons. The said clouds of electrons are possible places that the electrons could reside. Schrodinger's Quantum-Wave model is still an accepted model to this day.

1932

mlin30_4 — 2025-02-12 16:38:17 UTC

English Physicist, James Chadwick, who is also the student of Earnest Rutherford, discovered the neutron.