History of Atomic Theory - Video Flashcards

Vocabulary flashcards covering key terms and concepts from the History of Atomic Theory lecture.

Aristotle

Ancient Greek philosopher who proposed the four fundamental elements (earth, wind/air, fire, water) and whose ideas influenced thinking for centuries.

Four Elements

Earth, air (wind), fire, and water as the basic substances proposed by Aristotle.

Atomism

The idea that matter is composed of indivisible units called atoms.

Democritus

Greek philosopher who argued for atoms and void; an early proponent of atomism around 460 BCE.

Parmenides

Philosopher who argued that change is an illusion and that nothing comes from nothing.

Atom

From Greek 'atomos' meaning indivisible; proposed as the basic uncuttable unit of matter.

Void

Empty space through which atoms were thought to move.

Robert Boyle

17th-century chemist who advanced gas studies, built vacuum pumps, and promoted empirical science.

The Sceptical Chymist

Boyle’s 1661 work arguing that elements are primitive, simple bodies and foundational for modern chemistry.

Corpuscularism

Early idea of indivisible particles (corpuscles) proposed to explain chemical phenomena, though never directly observed.

Law of Conservation of Mass

Mass is neither created nor destroyed in ordinary chemical reactions.

Law of Definite Proportions

A given compound contains fixed ratios of elements by mass.

Law of Multiple Proportions

When elements form compounds, the ratios of the masses of one element combining with a fixed mass of another are simple whole numbers.

John Dalton

Early 19th-century chemist who proposed atomic theory and the law of multiple proportions.

Dalton’s Atomic Theory

Elements are made of atoms; atoms of the same element are identical; compounds form when atoms combine; chemical reactions rearrange atoms.

First Table of Atomic Masses

Dalton’s initial attempt to quantify atomic masses by comparison to a standard mass.

Avogadro’s Hypothesis

At the same temperature and pressure, equal volumes of different gases contain the same number of particles.

Gay-Lussac (Combining Volumes)

Gases combine in simple whole-number volume ratios; e.g., 2 H2 + O2 → 2 H2O.

Electron

Negatively charged subatomic particle; discovered via cathode rays; key to atomic structure.

J.J. Thomson

Physicist who discovered the electron and proposed the Plum Pudding Model; measured e/m ratio.

Plum Pudding Model

Atomic model with a positively charged ‘pudding’ containing embedded electrons like plums.

Rutherford

Ernest Rutherford; tested the plum pudding model and proposed a nucleus-centered atom after the gold foil experiment.

Nuclear Atom

Atom model with a dense, positively charged nucleus surrounded by electrons.

Proton

Positively charged particle located in the atomic nucleus.

Neutron

Neutral particle in the nucleus; discovered by James Chadwick in 1932.

Chadwick

James Chadwick; demonstrated the existence of the neutron.

Isotope

Atoms of the same element with the same number of protons but different numbers of neutrons.

Atomic Number (Z)

Number of protons in the nucleus.

Mass Number (A)

Sum of protons and neutrons in the nucleus.

Quantum Model (Planck, Einstein, Bohr, etc.)

Modern view of atomic structure incorporating quantization and wave-particle duality.

Planck

Physicist who showed energy is quantized and introduced the concept of quantums.

Planck’s Constant (h)

Constant linking energy and frequency (E = hν) in quantum theory.

Photon

Quantum of light; particle-like component of electromagnetic radiation proposed by Einstein.

Photoelectric Effect

Emission of electrons when light shines on a material; explained by photons.

Hydrogen Line Spectrum

Discrete emission lines from excited hydrogen; evidence for quantized energy levels.

Bohr Model

Hydrogen atom model with electrons in fixed orbits around the nucleus and quantized energy levels.

Quantum Mechanical Model

Modern atomic model using wave functions and orbitals to describe electron behavior.

Wave Functions

Mathematical description of an electron’s position and momentum in an atom.

Orbital

Region around the nucleus where an electron is likely to be found; related to energy level.

Uncertainty Principle

Fundamental limit on simultaneously knowing a particle’s position and momentum.

Heisenberg

Physicist who formulated the Uncertainty Principle and contributed to quantum mechanics.

de Broglie

Physicist who proposed matter waves, linking particle and wave behavior.

Schrödinger

Physicist who developed wave mechanics and the Schrödinger equation for atomic orbitals.

1s Orbital

The lowest-energy orbital in the quantum mechanical model for electrons.