The Atom

Early Atomists

100

This ancient Greek philosopher was the first to propose the existence of atoms

Democritus

200

This Greek philosopher disliked the notion of atomism because the existence of atoms necessarily requires the existence of vacuums

Aristotle

300

This philosopher, a follower of Democritus, integrated atomism with hedonistic ethics

Epicurus

400

This 17th-century French thinker interpreted atomism through a Christian perspective

Pierre Gassendi

500

This Roman poet expanded on atomism, arguing against free will, in his poetic work, On the Nature of Things

Lucretius

Early Scientists

100

This Italian scientist developed the first vacuum and barometer using a mercury tube.

Evangelista Torricelli

200

This demonstration involved two hemispheres that horses couldn't pull apart due to vacuum pressure.

Madgeburg Hemispheres

300

The first vacuum used a tube of this material turned upside down into a bowl

Mercury

400

This man founded modern chemistry, devised the Law of Conservation of Mass, and ended up beheaded by the French Revolution

Antoine Lavoisier

500

Although he lacked experimental evidence, this man hypothesized the Law of Conservation of Mass before Lavoisier

Benjamin Franklin

Chemical Laws

100

This law states no matter is created or destroyed in a chemical reaction.

Law of Conservation of Mass

200

This law says compounds are made of consistent ratios of elements.

Law of Definite Proportions

300

This law describes elements combining in whole number ratios when one has a fixed mass.

Law of Multiple Proportions

400

This scientist discovered the Law of Multiple Proportions and developed modern atomic theory

John Dalton

500

This scientist devised the Law of Definite Proportions

Joseph Proust

Atomic Models & Experiments

100

This subatomic particle discovered using a glass discharge tube after being repelled by a magnet

Electron

200

This experiment was used to find the mass-to-charge ratio of the electron

Oil drop experiment

300

This model proposed atoms as a positive mass with electrons spread like fruit in a dessert.

Plum pudding model

400

Ernest Rutherford shot alpha particles at this material, revealing the nucleus

Gold foil

500

Rutherford's model describes the atom as mostly empty space, with a dense positive core.

Nuclear model

Mass & Moles

100

This unit is used for atomic mass, based on carbon-12 being exactly 12.

Atomic mass unit (amu)

200

This is the number of particles in one mole, approximately 6.022 x 10²³

Avogadro's Number

300

Isotopes of an element differ by this number of subatomic particles

Neutrons

400

This is the weighted average of an element's naturally occurring isotopes.

Average atomic mass

500

Convert 1.8066 x 10²⁴ atoms of carbon to grams (approximately)

~36 grams