Development of Atomic Theory and Discovery of the Electron

Vocabulary flashcards covering early atomic models, quantitative chemical laws, Dalton's atomic theory, cathode ray experiments, and Thomson's plum-pudding model.

Democritus

Ancient Greek philosopher ($400\text{ B.C.}$) who proposed that nature's basic particle is the invisible atom.

Aristotle

Ancient Greek philosopher who proposed that matter is continuous and composed of earth, air, fire, or water.

Law of Conservation of Matter

Scientific law credited to Lavoisier stating that matter is neither created nor destroyed during chemical reactions.

Law of Definite Proportions

Law stating that chemical compounds are always formed from elements combined in fixed, small whole-number mass ratios.

Law of Multiple Proportions

Law stating that when elements combine to form different compounds, they combine in small whole-number ratios by mass.

John Dalton

English chemist who proposed a scientific atomic theory in $1808$ based on mass ratios and quantitative laws.

Dalton's Atomic Theory

Theory stating that matter consists of indivisible atoms, atoms of an element are identical, compounds form in small whole-number ratios, and reactions rearrange atoms.

Cathode Ray Tube (CRT)

An evacuated glass tube containing a cathode ($-$) and anode ($+$) used to create and study deflected cathode rays.

J. J. Thomson

Physicist who discovered the electron in $1897$ using cathode ray experiments, earning the Nobel Prize in Physics in $1906$.

Electron

Identical, negatively charged subatomic particles discovered by J. J. Thomson from deflected cathode rays.

Millikan

Physicist whose experiments established that every electron has the exact same charge, earning him the Nobel Prize in Physics in $1923$.

Plum-pudding model

Atomic model proposing that small negative electrons are distributed throughout a bulk, positively charged sphere.

Charge-to-mass ratio

A property of cathode rays measured by J. J. Thomson that remained identical regardless of the material used for the cathode.