Atomic theory

Leucippus and Democritus

Ancient Greek philosophers who introduced the concept of matter being composed of indivisible particles called "atomos."

Atomos

A term meaning "uncuttable," referring to the tiny particles that make up matter according to Leucippus and Democritus.

Law of Conservation of Mass

Proposed by Antoine Lavoisier, stating that mass remains constant despite changes in form.

John Dalton

Early 19th-century scientist who determined that elements exist as discrete packets of matter known as atoms.

Eugen Goldstein

Discovered positive rays (protons) in discharge tubes in 1886.

J.J

Discovered electrons using cathode rays and proposed the "plum pudding model" of the atom.

Plum Pudding Model

J.J. Thomson's model suggesting that electrons are distributed within a positively charged matrix.

Ernest Rutherford

Conducted the gold foil experiment in 1909, discovering the nucleus and concluding that atoms are mostly empty space.

Nucleus

A small, dense, positively charged center of an atom discovered by Ernest Rutherford.

Niels Bohr

Proposed the "planetary model" of the atom in 1913, where electrons orbit a central nucleus in specific energy levels.

Heisenberg Uncertainty Principle

Formulated by Werner Heisenberg, stating that it's impossible to know both the exact position and momentum of an electron simultaneously.

Quantum Theory

Proposed by Werner Heisenberg, suggesting that electrons exhibit properties of both particles and waves.

Cloud Model

The modern quantum model describing electrons in terms of probability, with orbitals representing regions where electrons are likely to be found.

Orbitals

Regions (s, p, d, f) in the cloud model where electrons are likely to be located, visualizing atoms as clouds with varying electron density.

Evolution of Atomic Theory

The progression from ancient philosophical ideas to a complex scientific model, incorporating key contributions and ongoing research.