History of the Periodic Table and Atomic Theory

Comprehensive vocabulary flashcards covering the history of the periodic table, early elemental discoveries, Democritus's ancient atomic philosophy, and John Dalton's atomic theory.

Ancient Elements

Elements known since antiquity—specifically gold, silver, platinum, and copper—which are located at the bottom of the reactivity series.

Alchemy

An early philosophical and proto-scientific tradition combining earth with air and fire that did not significantly advance the discovery of individual elements.

Henning Brand

The individual who, in 1649, became the first recorded person to discover a new element by boiling urine to isolate phosphorus.

Robert Boyle

Scientist who published Henning Brand's work in 1680 and defined an element as a substance that cannot be broken down into simpler substances by a chemical reaction.

Antoine Lavoisier

Known as the father of modern chemistry; authored the first modern chemistry textbook, "Elementary Treatise of Chem" (Elementary Treatise on Chemistry), which classified substances including $O$, $N$, $H$, $P$, $Mg$, $Zn$, $S$, light, and calories.

Johann Wolfgang Döbereiner

German chemist who created an early scheme to classify elements by grouping them into sets of three with related chemical properties, known as triads.

Döbereiner's Triads

Groups of three elements exhibiting similar properties identified by Johann Wolfgang Döbereiner, such as chlorine, bromine, iodine ($Cl$, $Br$, $I$); strontium, calcium, barium ($Sr$, $Ca$, $Ba$); and lithium, sodium, potassium ($Li$, $Na$, $K$).

Atomos

The Greek word meaning indivisible, proposed by Democritus to represent the fundamental particle of which all matter is made.

Democritus (460–370 BC)

Ancient Greek philosopher who proposed that matter is composed of indivisible fundamental particles called "atomos" moving through empty space.

Democritus' Ideas on Atoms

The philosophical concept that atoms are solid, homogeneous, indestructible, and indivisible, existing in different sizes and shapes that determine the properties of matter.

Democritus' Ideas on Changes in Matter

The principle that apparent changes in matter result entirely from changes in the groupings of atoms, not from transformations within the atoms themselves.

Aristotle's Opposition to Atomic Theory

Aristotle's rejection of Democritus's concept of the atom, which squelched atomic theory for thousands of years until the 1800s in favor of the four classical elements (earth, air, fire, water).

John Dalton (1766–1844)

An English schoolteacher and tutor who revived and scientifically revised Democritus's atomic concepts and developed Dalton's Law of Partial Pressures.

Dalton's Law of Partial Pressures

A gas law formulated by John Dalton during his experimental work isolating and studying gases.

Dalton's Atomic Theory (First Postulate)

All matter is composed of extremely small particles called atoms.

Dalton's Atomic Theory (Second Postulate)

All atoms of a given element are identical, possessing the exact same size, mass, and chemical properties.

Dalton's Atomic Theory (Third Postulate)

Atoms of a specific element are different from those of any other element.

Dalton's Atomic Theory (Fourth Postulate)

Different atoms combine in simple whole-number ratios to form chemical compounds.

Dalton's Atomic Theory (Fifth Postulate)

Atoms cannot be created, divided into smaller particles, or destroyed; in a chemical reaction, atoms are separated, combined, or rearranged.