Radiation Production and Characteristics - Atomic Theories

Vocabulary flashcards covering atomic theories, key discoveries, scientists, and subatomic structures from the lecture on Radiation Production and Characteristics.

Atomic Theory

The scientific theory of the nature of matter, stating that matter is composed of small particles called atoms.

Atomos

A Greek term meaning indivisible or uncuttable, coined by Democritus to describe the smallest, uncuttable piece of matter.

Democritus

A Greek philosopher who co-originated the idea in 442 BC that all matter is composed of small, hard, indivisible particles called atomos.

Aristotle

An ancient Greek philosopher who declared that all matter was made of four elements (fire, air, water, Earth) and four properties (hot, cold, dry, wet).

Solid Sphere Model

An atomic model proposed by John Dalton in 1808 depicting atoms as solid, indivisible spheres that combine in ratios by weight.

Crookes Tube

An early type of vacuum tube constructed by Sir William Crookes in 1870 that led to the discovery of cathode rays.

Wilhelm Conrad Roentgen

A German physicist who discovered X-rays on November 8, 1895, after observing chemical fluorescence caused by cathode rays.

Electron

A negatively charged subatomic particle discovered in 1897 by J.J. Thomson using the properties of cathode rays.

Plum Pudding Model

An atomic model proposed by J.J. Thomson in 1904 depicting an atom as a uniform, positively charged sphere with electrons embedded inside.

Radioactivity

A phenomenon, coined by Marie Curie, in which certain elements spontaneously emit radiation as radioactive particles cause atoms to break down.

Max Planck

A physicist who introduced quantum theory in 1900, stating that electromagnetic energy is emitted in discrete units called quanta or photons.

Robert Millikan

An American physicist who measured the elementary charge of a single electron between 1908 and 1917.

Gold Foil Experiment

An experiment conducted by Ernest Rutherford observing alpha particle scattering, which demonstrated the existence of the atomic nucleus.

Nuclear Model

An atomic model proposed by Ernest Rutherford (1909–1911) featuring a small, dense, positively charged nucleus surrounded by scattered electrons.

Bohr Atomic Model

An atomic model developed by Niels Bohr in 1913 showing electrons orbiting the nucleus in discrete energy levels and releasing photons when jumping to lower orbitals.

Schrödinger Equation

A mathematical equation formulated by Erwin Schrödinger in 1926 that describes how electrons move in waveforms and how quantum systems change over time.

Neutron

A neutral subatomic particle located in the atomic nucleus, discovered by James Chadwick in 1932.

Nuclear Fission

The process of splitting an atomic nucleus, discovered in 1938 by Otto Hahn and Lise Meitner.

Glenn Seaborg

A scientist who contributed to discoveries of transuranium elements and nuclear medicine applications, including the development of I-131 for thyroid disease.

Quarks

Elementary subatomic particles with no substructure proposed by Murray Gell-Mann and George Zweig in 1964 that combine to compose protons and neutrons.

Electron Cloud Model

The 20th-century modern atomic model stating that electrons move at high speeds in an electron cloud around the nucleus based on their energy levels.