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460 BCE
Democritus
Democritus created first theory of atom, although some believe it was Leucippus who shared his ideas with Democritus,
he started the atom theory by suggesting that all matter consisted of tiny, indivisible particles. He explains the universe through atoms and voids. -
384 BCE
Aristotle
Aristotle, an ancient Greek philosopher, did not believe in the atomic theory, he believed everything was made of a combination of the 4 elements -
Antoine Lavoisier
Antoine Lavoisier was born in Paris, France. He found that mass is conserved in a chemical reaction through experimenting. He proposed combustion theory which was based on mass measurements as he experimented with phosphorus & sulfur, he showed that each gained weight when combined with air.He also isolated/named hydrogen and oxygen, and predicted the later discovery of silicon. -
Joseph Louis Proust
A french chemist born in France, Proust published Law of Definite Proportions in 1974, which says a compound has exact proportions of an element by mass based on his observations on the composition of chemical compounds -
John Dalton
John Dalton was born in the UK. He proposed that all matter is composed of atoms and are invisible/ indestructible building blocks, and have diff. size and mass. He experimented with gases; and hypothesized the mass/ size of the gases and determined that chemical elements are composed atoms. He was a chemist, meteorologist, and physicist -
Billiard Ball Model
The Billiard Ball model All substances are made of atoms. Atoms can’t be divided s, created, or destroyed. Different element atoms have diff. masses. Atoms put together form compounds,
Dalton investigated pressure and other properties of gases& inferred that gases must consist of tiny, individual particles that are in constant, random motion. -
JJ Thomson
Thomson was born Manchester, United Kingdom
He created the positive and negative ions theories and went on to received the Nobel Prize in Physics -
Max Planck
Planck was the originator of the quantum theory of energy. Einstein used Planck's quantum theory to describe the particle properties of light. -
Marie Curie
Marie Curie grew up in Warsaw, Poland. She went on to discover radioactivity (elements polonium and radium) by working with a mineral pitchblende.Curie conducted experiments on uranium rays, radioactive elements, she also developed X- Ray machines. She was also the first woman to win Nobel Peace prize. -
Ernest Rutherford
In Brightwater, New Zealand, Rutherford discovered that atoms have a small charged nucleus surrounded by largely empty space, and are circled by tiny electrons. -
Albert Einstein
Born in Ulm, Germany, Albert discovered that energy and mass are interchangeable and created the equation E=mc2. He created the theory of relativity by calculating how the movement of molecules in a liquid can cause the Brownian motion.
“Life is like riding a bicycle. To keep your balance you must keep moving.” -
Bohr Model
In 1913, Niels Bohr, a danish physicist, proposed a theory for the hydrogen atom. Bohr was the first to discover that electrons travel in separate orbits around the nucleus and that the number of electrons in the outer orbit determines the properties of an element.
Danish physicist The Bohr Model is a planetary model in which the negatively-charged electrons orbit a small, positively-charged nucleus similar to the planets orbiting the Sun -
Quantum model (Erwin Schrödinger)
Schrödinger used mathematical equations to describe the likelihood of finding an electron in a certain position. This atomic model is known as the quantum mechanical model of the atom. -
James Chadwick
Born in the United Kingdom, Chadwick discovered the Neutron in atoms and later went on to receive the Nobel Prize in Physics. -
Plum pudding model
J.J. Thomson discovered the electron by experimenting with a Crookes, or cathode ray, tube and created the positive and negative ions theories. The atom is composed of electrons surrounded by a soup of positive charge to balance the electrons negative charges, such as negatively charged plums. -
Werner Heisenberg
Born in Würzburg, Germany, Heisenberg was know for his uncertainty principle and theory of quantum mechanics, he was awarded the Nobel Prize for Physics for his subsequent research and application of this principle. -
Lucas Model
This model predicts the "magic numbers" 2, 8, 18, and 32 of electrons in the filled shells and also is able to predict why the Periodic Table of the Elements has exactly seven rows. The Lucas model also predicts the structure of the nucleus and correctly predicts hundreds of nuclide spins. Joeseph Lucas was born on April 12, 1834, in Hockley, Birmingham, United Kingdom -
Robert Oppenheimer(father of atomic bomb)
Born in New York City, NY, Robert Oppenheimer, a technical director of the Manhattan Project was present during the creation of the first atomic bomb. Nuclear fission produces the atomic bomb -
Ernest Rutherford
Ernest Rutherford gets the Nobel Prize in Chemistry for his theory of atomic structure. -
Chadwick
Chadwick discovered that Beryllium, when bombarded by alpha particles, emitted a very energetic stream of radiation. -
Joseph Louis Proust
Joseph Louis Proust published Law of Definite Proportions
