Honors Chemistry - Early Ideas

Early Ideas About Matter

Main Idea: Chapter 4-1

The ancient Greeks tried to explain matter, but the scientific study of the atom began with John Dalton in the early 1800s.

Key Concepts

Democritus was the first person to propose the existence of atoms.
According to Democritus, atoms are solid, homogeneous, and indivisible.
Aristotle did not believe in the existence of atoms.
John Dalton’s atomic theory is based on numerous scientific experiments.

Dewitt: Models of the Atom Timeline

This video is about the different ways that scientists have pictured the atoms over the years. It starts with Democritus and Leucippus, the first philosophers to discuss atoms. Then John Dalton did experiments on atomic theory. J.J. Thompson proposed the plum pudding model of the atom when he discovered electrons, and Ernest Rutherford countered with the nuclear atom when he discovered the nucleus in the gold foil experiment. Niels Bohr imagined that electrons circled the nucleus in orbits, and Erwin Schrodinger's quantum mechanical model pictures electrons buzzing around in orbitals.

The 2,400-year search for the atom

How do we know what matter is made of? The quest for the atom has been a long one, beginning 2,400 years ago with the work of a Greek philosopher and later continued by a Quaker and a few Nobel Prize-winning scientists.

Atomism & the Greek theorists (ancient models of the atom):

450 BC: Leucippus & Democritus of Abdera (solid sphere model of the atom)

The theory of Democritus held that everything is composed of "atoms", which are physically, but not geometrically, indivisible; that between atoms, there lies empty space; that atoms are indestructible, and have always been and always will be in motion; that there is an infinite number of atoms and of kinds of atoms, which differ in shape and size.

400 BC: Empedocles, Aristotle, Plato (Alchemy)

Classical elements typically refer to the concepts of earth, water, air, fire, and (later) aether, which were proposed to explain the nature and complexity of all matter in terms of simpler substances