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700 BCE
Atomic Theory in India
In India, it was believed that the first idea for the atomic theory was created by a Hindu sage called Aruni, who was a philosopher who questioned how could things hold together having mass. This was later improved talking about how each atom have their own unique motion, colour, and smell. -
500 BCE
Original Atom Theory
Greek Philosopher Leucippus of Miletus came up with the idea that all matter was created by small things called atoms. The word "atom" comes from the Greek word "indivisible". This occurred sometime in the 5th century BCE. -
494 BCE
Empedocles
Influenced by Aristotle and Pythagoras, he began creating philosophies of his own, which spurred the start of alchemy. He believed that there were 4 elements: Earth, Fire, Water and Air. He also believed in "Love and Strife" (Love and Hatred) which he used to explain the process of mixture and separation. He lived from approximately 494 BCE - 434 BCE. -
460 BCE
Democritus
Democritus lived from 460 BCE - 370 BCE~ and was also called "The father of modern science" as he helped develop the basics for the atomic theory He stated:
- Between atoms, there is empty space
- Atoms are indestructible
- Atoms are constantly moving
- There are an infinite amount of atoms and kinds of atoms -
601
Alchemy
Alchemy has also been believed to be created in Egypt, where they believed that there were life and death within the Nile, which created the thought of creating things from nothing. This also spurred the legend of the Philosopher Stone, which was supposed to turn any base metal into gold. -
John Dalton's Atomic Theory
In 1803, Dalton was inspired by Democritus' suggestion and created his own atomic theory stating:- All mater is made of atoms.
- All atoms of an element have the same mass and properties
- Compounds are formed by two or more different atoms
- A chemical reaction is the rearrangement of the atoms
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J.J. Thomson
Thomson discovered the electron in 1894, through the use of cathode-ray tubes. Thomson also contributed to the atomic theory by his Plum-Pudding Model in 1904 where he proposed electrons and positively charged particles were mixed together, creating a blend like plum-pudding. -
Marie Curie
Marie contributed to the atomic theory by discovering uranium, polonium, and radium. She also contributed to the atomic theory by discovering radioactivity, which was a revolutionary discovery at the time. She realized that radioactivity was not because of how the atoms are arranged, but it is produced by the atom itself. -
Max Planck
Discovered that these "black bodies" radiated a specific proportion of the energy absorbed according to the frequency. This is now known as Planck's constant. He also discovered that this energy came in specific packets, and that all energy was a certain number of these packets. -
Hantaro Nagaoka
Nagaoka was a Japanese physicist which created the Saturnian model, which described the positions of atoms as having a positively charged center, with having electrons circle around the nucleus (like Saturn's rings). He also believed that the nucleus was large and the electrons were small. -
Albert Einstein
Held a major role in the development of physics and chemistry in the 20th century. In 1905, he discovered the famous equation E = mC^2, which means that energy can be created from matter equivalent to its mass times the speed of light squared. This equation is what eventually brought forth the creation of the atomic bomb. The other invention that he had has his Theory of Relativity, which he released in 1915, stating that gravity can curve according to the geometrical shape. -
Ernest Rutherford
Rutherford's contribution to the atomic theory is through his discovery of a dense nucleus from his gold foil experiment, where the light was refracted due to the alpha rays hitting the nucleus. From this experiment, he was able to disprove Thomson's model and create his own planetary model of an atom, where the neutrally and positively charged atoms were in the nuclear and the outside were the electrons. -
Niels Bohr
When working with Rutherford, in 1913 Bohr came up with his own model for the atomic theory, stating that there are different energy levels, represented by shells. He also stated that when electrons jump to a lower level, it produces light, explaining why atoms produced specific wavelengths of light. -
Louis de Broglie
In 1924, deBroglie released his thesis on the motion of the wavelengths and eventually devised an equation stating that a wavelength is released whenever a particle is moving, proportional to its mass and velocity (as well as Planck's constant). -
Wernr Heisenberg
Created the Heisenberg Uncertainty Principle which states that it is not possible to find the position and the momentum on a particle at the same time with high precision. Heisenberg is also known for being one of the early members which helped contribute to quantum mechanics. -
Wolfgang Pauli
Was one of the pioneers in quantum physics. Created the Pauli Exclusion Principle, which states that no two electrons can have the same four quantum electron numbers. This means that since there are only two electrons with an orbit, they have to have opposing spins from each other. -
Erwin Schrödinger
Erwin Schrödinger contributed to the atomic theory through his mathematical skills, as he believed that electrons did not follow a single path, and then derived an equation to show that electrons can exist anywhere within a certain area depending on its charge, called the quantum mechanical model. -
James Chadwick
Contributed to the atomic theory by discovering that neutrons exist together with the protons, contributing to the mass in the center of an atom. With this discovery, chemists were able to build a somewhat accurate representation of an atom. -
Gerhard Herzberg
Was born in Germany but moved to Canada during WWII. Researched in the geometrical shape and structure of atoms with odd number of electrons. This became the base of molecular spectroscopy, which is the study of how atoms absorb and reflect light. -
Henry Taube
Born in Saskatchewan and tutored by Gerhard, he eventually went to study how the free electrons within metals affected the reaction rate and reaction itself in oxidation processes. -
Maria Goeppert Mayer
In the late 1940's Mayer proposed a nuclear shell model, in which she used Pauli exclusion principle (no 2 electrons may hold different spins, unless all spins of the same type is fulled in other shells) in order to try explain why certain configurations of neutrons in the nucleus creates stable atoms. -
John Charles Polanyi
Born in England, where he was sent to Toronto in order to be safe from the bombing of the war. He also studied under Gerhard and used his molecular spectroscopy base in order to do his own research. He studied chemical reactions where light was emitted in order to track the location of each atom. -
Robert LeRoy
Is a teacher at Waterloo, where he created the Leroy-Bernstein theory and the LeRoy radius, where that defines the distance between two nuclei using vibration energy levels.
