The History of the Atom: Atomic Theory

Vocabulary flashcards covering the key scientists, experiments, discovery years, and atomic models in the history of atomic theory.

Democritus

A Greek philosopher who in 400 BCE was the first to propose the idea of the atom and named it from the Greek word "atomos".

Atomos

The Greek word meaning "uncuttable," from which the term "atom" was derived.

John Dalton

The scientist who provided the first scientific proof of the atom in 1804 through the Law of Multiple Proportions and proposed the solid sphere model.

Law of Multiple Proportions

The type of experiment conducted by John Dalton in 1804 that provided the first scientific proof of the atom.

Solid Sphere Model (Billiard Ball Model)

John Dalton's atomic model that represents atoms as tiny, solid, indivisible spheres.

Dalton's Postulate on the Nature of Matter

The principle stating that all matter is made of tiny, solid, indivisible balls called atoms.

Dalton's Postulate on Elements

The principle stating that atoms of the same element are identical in mass and properties, while atoms of different elements have different masses and properties.

Dalton's Postulate on Indivisibility

The principle stating that atoms cannot be subdivided, created, or destroyed.

Dalton's Postulate on Chemical Compounds

The principle stating that atoms combine in whole-number ratios to form compounds.

Dalton's Postulate on Chemical Reactions

The principle stating that atoms are rearranged during chemical reactions and are not created or destroyed.

JJ Thomson

The scientist who discovered the electron in 1897 using a cathode ray tube experiment and proposed the Plum Pudding model.

Cathode Ray Tube Experiment

The experiment conducted by JJ Thomson in 1897 that led to the discovery of the electron.

Plum Pudding Model (Chocolate Chip Cookie Model)

JJ Thomson's atomic model depicting negatively charged electrons embedded within a sphere of positive charge.

Robert Millikan

The scientist who discovered the charge and mass of the electron in 1909 using the Oil Drop Experiment without altering the atomic model.

Oil Drop Experiment

The experiment conducted by Robert Millikan in 1909 that determined the specific charge and mass of the electron.

Ernest Rutherford

The scientist who in 1911 conducted the gold foil experiment and discovered the proton, dense nucleus, and that the atom is mostly empty space.

Gold Foil Experiment

The experiment conducted by Ernest Rutherford in 1911 that revealed the dense nucleus and demonstrated that the atom is mostly empty space.

Nuclear Model

Ernest Rutherford's atomic model featuring a small, dense nucleus surrounded by empty space containing electrons.

Neils Bohr

The scientist who discovered discrete energy levels and electron orbitals in 1913, proposing the Planetary Model of the atom.

Planetary Model

Neils Bohr's atomic model in which electrons orbit the nucleus in discrete circular energy levels or orbitals.

Heisenberg and Schrodinger

Scientists who developed the Quantum Model (Electron Cloud Model) of the atom in 1926 based on the Uncertain Relation.

Uncertain Relation

The concept or experiment investigated by Heisenberg and Schrodinger in 1926 that led to the development of the Electron Cloud Model.

Quantum Model (Electron Cloud Model)

The atomic model developed by Heisenberg and Schrodinger in 1926 that depicts electrons existing within probability clouds rather than fixed orbits.