Introduction to Chemistry

Democritus

thought of the smallest part of matter and coined the term “atomos”. It cannot be divided

John Dalton

viewed the atom as a small solid sphere. Came up with the “billiard ball model”. Developed the atomic theory.

• atoms are indivisible

• atoms of the same element are exactly alike (they have the same mass)

• atoms of different elements can join to form compounds

J. J. Thomson

he experimented with the Cathode Ray Tube. Found that small negatively charged particles (electrons) are inside the atom. Developed the Plum Pudding Model.

Henri Becquerel

discovered radiation by accident. This was later used to study atoms structure. Uranium released radiation called alpha particles.

Robert Millikan

measured the charge of a single electron to be -1.6 × 10^-19 Coulombs. Famous for the oil drop experiment.

Ernest Rutherford

performed the gold foil experiment. He discovered a tiny and positive nucleus within the atom. The nuclear model.

Neils Bohr

Developed the theory that electrons orbit the nucleus in energy levels. Made the Planetary Model

Erwin Schrödinger

electrons travel in waves within regions of space called orbitals. Came up with the wave model.

James Chadwick

discovered the neutron. Heavy particles in the nucleus with no charge.

Orbital

a region in a space that describes the probable location of an electron