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460 BCE
Democritus
Democritus was a greek philosopher, a central figure in the development of philosophical atomism and of the atomic theory. He was the first one who proposed that everything in the world is made up of tiny particles, surrounded by empty space. He conceived of the Void as a vacuum, an infinite space in which moved an infinite number of atoms that made up Being. These atoms are eternal and indivisible, they're so small that their size cannot be diminished (hence the name atomon, or "indivisible"). -
Period: 390 BCE to
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Atoms would be all forgotten until 1808 when a Quaker teacher named John Dalton sought to challenge Aristotelian theory. -
384 BCE
Aristotle
Aristotle was born in Macedonia, northern Greece. His father was the physician of Amyntas III, king of Macedonia and grandfather of Alexander the Great. He was Plato's pupil for 20 years. According to Aristotle, the universe is composed of 4 fundamental elements, which are fire, water, earth and air. He adopted this view from Empedocles, a presocratic predecessor. Each element was characterised by elementary qualities: heat, cold, wetness and dryness. -
John Dalton
John Dalton was an English meteorologist and chemist, a pioneer in the development of modern atomic theory. He developed a method to measure the masses of the elements in a compound. His law of multiple proportions states that when two elements form more than one compound, masses of one element that combine with a fixed mass of the other are in a ratio of small whole numbers. -
A New System of Chemical Philosophy by John Dalton
John Dalton extended Proust's work and converted the atomic philosophy of the Greeks into a scientific theory Between 1808 and 1810. His book "A New System of Chemical Philosophy" was the first application of atomic theory to chemistry. Also, he was one of the fathers of Chemical Experimentation. -
Erwin Schrödinger
Born in the capital of Austria, Erwin Schrödinger was a theoretical physicist, who came up with the wave theory of matter and other important areas of quantum mechanics. -
Sir Joseph John Thomson
Thomson was an English physicist who contributed to revolutionising the knowledge of atomic structure through his discovery of the electron (1897). He received the Nobel Prize for Physics in 1906. Known as the chocolate chip cookie model of the atom, he showed atoms as uniformly packed spheres of positive matter, filled with negatively charged electrons. -
Photoelectric effect - Albert Einstein
The photoelectric effect is a ray of particles (photons) whose energies are related to their frequencies.
This experiment consisted of shooting these rays (light) directly onto a steel slide. And when the photons hit the metal, the photons collide with the atoms. And if the frequencies are high enough, the photons will knock off an electron of the metal slide. -
Ernest Rutherford
New Zealand-born British physicist. As a pupil of J.J. Thomson, he was the central figure in the study of radioactivity, and with his idea of the nuclear atom, he led the investigation of nuclear physics.
He won the Nobel Prize for Chemistry in 1908. -
The father of the nuclear age
Rutherford had become known as the father of the nuclear age.
He decided to investigate atoms more closely by shooting small, positively charged alpha particles at a sheet of gold foil. While most of the particles pass through, some bounced right back, suggesting that the foil was more like a thick net with a very large mesh.
He concluded that atoms consisted largely of empty space with just a few electrons, while most of the mass was concentrated in the center, which he termed the nucleus. -
Bohr's Atomic Model
Bohr's first contribution to the new idea of quantum physics started in 1912. He stipulated that electrons orbit the nucleus at fixed energies and distances, able to jump from one level to another, but not to exist in the space between. Bohr's planetary model took center stage, but soon, it too encountered some complications. His experiments had shown that rather than simply being discrete particles, electrons simultaneously behaved like waves. -
Albert Einstein
Albert Einstein was a german physicist, who later worked for The United States government during World War II, and continued being a teacher.
He developed the special and general theories of relativity and won the Nobel Prize for Physics in 1921 (photoelectric effect).
He is also considered the most influential physicist of the 20th century. -
Niels Bohr
Neils Bohr was a Danish physicist. Bohr did expand Rutherford's nuclear model, drawing on earlier work by Max Plank and Albert Einstein. He was the first to restrict the energy of a system, to the problem of atomic and molecular structure. Because of this work, he won the Nobel Prize for Physics in 1922. -
Heisenberg's Uncertainty Principle
And in formulating his famous uncertainty principle, it was impossible to determine both the exact position and speed of electrons as they move around an atom. -
Werner Heisenberg
Heisenberg was a German physicist and philosopher who discovered a way to formulate quantum mechanics. For that discovery, he was awarded the Nobel Prize for Physics in 1932.
He is best known for his uncertainty principles, which were published in 1972.
He also made important contributions to the theories of the hydrodynamics of turbulent flows, the atomic nucleus, ferromagnetism, cosmic rays, and subatomic particles -
Schrödinger's cat
Schrödinger's cat is an experiment which consists of a cat, that is locked in a steel box with a small amount of radioactivity substance.
If the atom decomposes, a device smashes a vial of poisonous gas, killing the cat.