Untitled Flashcards Set

Democritus (400 BCE)

• Definition: Ancient Greek philosopher who proposed that matter is composed of indivisible particles called "atomos," meaning "indivisible."

Aristotle (350 BCE)

• Definition: Greek philosopher who rejected Democritus' atomic theory and believed that matter was continuous and composed of four elements: earth, water, air, and fire.

John Dalton (1803)

• Definition: English chemist and physicist who developed the modern atomic theory, stating that atoms are indivisible and indestructible particles that make up matter and combine in fixed ratios to form compounds.

Eugen Goldstein (1886)

• Definition: German physicist who discovered the existence of positive particles in atoms (protons) through his work with cathode rays.

Henri Becquerel (1896)

• Definition: French physicist who discovered radioactivity by observing the spontaneous emission of radiation from uranium salts.

J.J. Thomson (1897)

• Definition: British physicist who discovered the electron and proposed the "plum pudding" model of the atom, where negatively charged electrons are embedded in a positively charged "pudding."

Ernest Rutherford (1899, 1911)

• Definition: New Zealand-born physicist who discovered the nucleus through his gold foil experiment and proposed the nuclear model of the atom, with a dense, positively charged nucleus surrounded by electrons.

Marie Curie (1902)

• Definition: Polish-French physicist and chemist who conducted pioneering research on radioactivity, discovering the elements polonium and radium.

Robert Millikan (1910)

• Definition: American physicist who measured the charge of the electron through his oil drop experiment, providing the first accurate value for the electron's charge.

Niels Bohr (1913)

• Definition: Danish physicist who developed the Bohr model of the atom, proposing that electrons orbit the nucleus in fixed energy levels or shells.

Louis de Broglie (1924)

• Definition: French physicist who proposed the wave-particle duality of matter, suggesting that particles such as electrons exhibit both wave-like and particle-like properties.

Erwin Schrödinger (1926)

• Definition: Austrian physicist who developed wave mechanics and the Schrödinger equation, which describes the behavior of electrons as wave functions.

James Chadwick (1932)

• Definition: British physicist who discovered the neutron, a neutral particle in the nucleus of the atom, contributing to the understanding of atomic structure.