A History of the Atom: Theories and Models

Vocabulary terms and key concepts covering the historical progression of atomic models and theories, including Dalton, Thomson, Rutherford, Bohr, and Schrödinger.

Atomos

The Ancient Greek word meaning indivisible, from which the modern word 'atom' is derived.

Solid sphere model

The atomic model proposed by John Dalton in 1803, stating that atoms are indivisible, atoms of a given element are identical, and compounds are combinations of different types of atoms.

John Dalton

The scientist who proposed the solid sphere model in 1803, recognising that atoms of a particular element differ from those of other elements.

Corpuscles

The term originally used by J.J. Thomson to describe electrons when he discovered them within atoms in 1897.

Plum pudding model

The atomic model created by J.J. Thomson in 1904, portraying the atom as composed of electrons scattered throughout a spherical cloud of positive charge.

J.J. Thomson

The Nobel Prize-winning scientist who discovered electrons in 1897 and formulated the plum pudding model of the atom in 1904.

Nuclear model

The atomic model proposed by Ernest Rutherford in 1911, which established that the atom is mostly empty space with its positive charge concentrated in the central nucleus.

Ernest Rutherford

The scientist who fired positively charged alpha particles at a thin sheet of gold foil in 1911, proving that the positive charge of an atom is localised in a central nucleus.

Nucleus

The central region of an atom where positive charge is concentrated, identified by Ernest Rutherford after some alpha particles deflected at large angles during his gold foil experiment.

Planetary model

The atomic model formulated by Niels Bohr in 1913, which describes electrons moving around the nucleus in orbits of fixed sizes and energies.

Niels Bohr

The physicist who modified Rutherford's model in 1913 by proposing stable, quantised electron orbits to explain the emission spectra of elements.

Quantised electron energy

A principle in Niels Bohr's atomic model stating that electron energies are restricted to fixed levels, preventing electrons from possessing energy values between those levels.

Quantum model

The atomic model developed by Erwin Schrödinger in 1926, which states that electrons move in waves and exist within probability clouds rather than fixed orbital paths.

Erwin Schrödinger

The physicist who proposed the quantum model in 1926, demonstrating that electron position cannot be precisely known and that electrons travel in waves rather than set orbits.

Orbitals

Clouds of probability in Erwin Schrödinger's quantum model that denote the regions where an electron is most likely to be found.