ATOMIC THEORY - GEN CHEM 1 (PRE-LIMS)

Democritus (Greek Philosopher)

In 400 BCE, he developed the fundamental of atom and its concept.

“All matter is composed of tiny, indivisible particles called atomos/atoms”

Aristotle (Greek Philospher)

Around 400 BCE, he did not believe in atomic theory. But he said that..

“All matter was composed of 4 elements: Earth, Water, Air and Fire”

John Dalton (English Chemist, Physicist, Meteorologist)

In 1803, he has the same thought with Democritus but he also said tha

“Atoms is the basic building blocks of matter”

Joseph John “JJ” Thompson (British Physicist)

In 1897, he studied the nature of cathode rays where he said that:

“Atoms are spheres of positive charge with negatively charged electrons embedded within, like plums in a pudding”

Ernest Rutherford (British Physicist, Scientist)

He’s the father of Nucleic Age, in 1911 he used his Gold Foil Experiment who discovered the Alpha and Beta Rays as positively and negatively charged raditaion and he said that:

“Atoms are mostly empty space, with a tiny dense, positively charged nucleus at the center, negatively charged electrons orbit this nucleus”

Niels Bohr (Danish Physicist)

In 1914, he discovered the Bohr Model. He said that:

“Atoms have electrons orbiting the nucleus in specific, quantized energy levels or shells”

Werner Heisenberg (German Physicist)

In Mid 1920s, he understand the atom through his development of matrix mechanics. He said that:

“The behavior of elecyrons within an atom is more accurately described as a cloud of probabilities rather than fixed orbits”

Matrix Mechanics

A Mathematicsl framework for quantumn mechanics (for formulation of uncertainty principles)

Wilhelm Conrad Roentgen (German Physicist) - 1845 to 1923

He discovered the x-ray to detect electromagnetic radiation in a wavelength range.

Henri Becquerel (French Physicist) - 1862 to 1908

He is the father of radiacivity. He discovered radioactivity of uranium that is shared in 1903 nobel price.

Robert Milikan (American Physicist) - 1868 to 1953

He published the oil-drop experiment. He detemined the actual charge of electron that is slightly lowered from the original.

His work: 1.592 × 10^-19 caulomb

Original: 1.602 × 20^-19 caulomb