-
Period: 495 BCE to 435 BCE
Empedocles
Empedocles is famous for his contribution to the atomic theory, he devised a theory that all substances are made up from the four elements, air, water, fire, and earth. -
Period: 460 BCE to 370 BCE
Democritus
Democritus was a renowned mathematician, he was famous throughout his era being a very intelligent person. However, he is best known for his contributions to the atomic theory. -
440 BCE
Empedocles
The theory that he argued of four elements being the building block to humanity was actually pondered upon by many philosophers before him. One philosopher thought that water was the substance that made everything up, another thought air, and another thought fire. Empedocles was the first to consider all four substances making up everything. -
390 BCE
Democritus
Democritus is famous for proposing his theories about the atom, leagues ahead of his time. He proposed that:
- Everything is composed of atoms which are indivisible
- Between atoms, there lie empty space.
- Atoms are indestructible
- Atoms have always been and always will be in motion -
1350
Alchemists
The alchemists lived in a time where they were shunned and looked down upon due to people thinking that they were performing black magic. They are stated to experiment with influencing the elements by changing base metals into gold. They have also revolved around the reconstruction and deconstruction of matter, through the four elements, Fire, Earth, Water, Air. This aided future scientist to analyze and discover the periodic table of elements. -
Period: to
John Dalton
John Dalton is famous because of the laws he introduced after the discovery of the atom. His laws stand true to this day. He introduced the atomic theory into chemistry, and he is known for his research into color blindness. -
John Dalton
John Dalton's Laws of Atomic Theory
- Matter is made up of indivisible particles called atoms
- Atoms of an element are identical
- Atoms can not be created or destroyed
- Atoms of different elements can form simple compounds
Dalton discovered his theory in 1803 -
Period: to
J. J. Thomson
J. J. Thomson is famous for discovering the electron by experimenting with cathodes ray tube. He also created his own diagram of the atomic structure shown as "plum pudding". The negative electrons were the raisins on top and the dough contained the positive electrons. -
Period: to
Max Planck
Max Planck was a German theoretical physicist who worked with quantum theory and quantum relativity. He produced his own theory that accurately predicts the spectral density of electromagnetic radiation. -
Period: to
Hantaro Nagaoka
Hantaro Nagaoka was a Japanese physicist and became one of the pioneers to Japanese physics during the Meiji period. In 1904 he developed a Saturnian model of the atom which was the first model to contain a nucleus. His discovery would soon be recognized by Rutherford in 1911 which spearheaded Rutherford's experiments. -
Period: to
Marie Curie
Marie Curie was a French physicist and chemist who conducted research into radioactivity. She was the first woman to win a Nobel Prize and she also won it twice. It is because of her discovery that we have radiation therapy today. She did this by discovering that tumor cells, when exposed to radium were destroyed faster than normal cells. -
Period: to
Ernest Rutherford
Ernest Rutherford was the apprentice to J.J. Thomson and he is famous for creating his own version of the atom which was different from Thomson's model because Thomson forgot to account for the positive electrons in the model. -
Period: to
Lise Meitner
Lise was born in Austria and became a physicist whose work was solely based off of radioactivity. Lise led a small group of physicist to discover nuclear fission of uranium when it absorbed an extra neutron. She discovered the the uranium atom would split when bombarded by neutrons. -
Period: to
Albert Einstein
Einstein was the son of a Jewish electrical engineer in Germany. His theories of special and general relativity changed man kind's view of the world drastically. He also worked with particle and energy theory which helped make quantum mechanics possible which also led to the atomic bomb. -
Period: to
Niels Bohr
Niels Bohr is famous for creating his own diagram of the atom. He proposed that the electron travels in orbits around the nucleus and when the electrons jump to another orbit, a light quantum is created. -
Period: to
Erwin Schrödinger
Erwin Schrödinger was a Austrian physicist who was known for his development of an "Electron Cloud Model" in 1926. His model consisted of a highly dense nucleus with electrons in varying orbitals (energy levels). He took Bohr's model one step further by using mathematical equations to determine the likelihood of finding an electron in a certain position. -
Period: to
James Chadwick
James Chadwick contributed to the atomic theory by discovering that neutrons exists in the atom. He discovered that neutrons exist at the center of an atom in the nucleus along with the protons. -
Period: to
Louis De Broglie
Louis De Broglie was an French physicist, who is famous for his work in quantum theory. More specifically, he discovered the wave nature of electrons and suggested that all matter has wave properties. -
Period: to
Satyendra Nath Bose
Satyendra was a Indian theoretical physicist. He is known for his work in quantum mechanics. In the early 1920s he provided the foundation Bose-Einstein statistics and the theory of Bose-Einstein condensate. He also gave the concept of Boson. His work was also further brought forward by Einstein which developed the Bose-Einstein theory. -
J. J. Thomson
J. J. Thomson discovered the electron inside of the atom and he proposed the plum pudding model of the atom which will later be proved to be wrong
Thomson discovered his theory in 1897 -
Marie Curie
Marie Curie is most famous for discovering the elements polonium and radium. She also discovered radioactivity by doing experiments with uranium. Her husband and her ended up sharing a Nobel Prize at that time for the discovery of the two elements. She is an important figure the in world of chemistry because at that time, the scientific field was mostly dominated by men and women were cast away, but Marie ended up winning two Nobel Prizes and taught at a school which was exclusively for men. -
Max Planck
Planck contributed to the atomic theory by producing his own equation called the Planck's constant. He derived this equation by postulating the idea that the energy of light is proportional to the frequency. His work also helped Albert Einstein to discover photons or light existing in discrete quanta of energy. -
Period: to
Wolfgang Pauli
Wolfgang Pauli was born in Austria in 1900. He was a theoretical physicist and one of the pioneers of quantum mechanics. Over his lifetime, he discovered Pauli's exclusion principle which formed the bias of the structure of matter and the whole of chemistry. He was also great friends with Niels Bohr and Werner Heisenberg. -
Period: to
Werner Heisenberg
Heisenberg is best known for his uncertainty principle, and theory of quantum mechanics. Some people said that he was ahead of his time being one of the smartest in his class and discovering his theories at the young age of 23! -
Hantaro Nagaoka
In 1904, Hantaro Nagoaka developed his own model of the atom and it was named the Suturnian system. the atom in the model was unstable from the beginning because by radiating continuously, the electron would continue to lose energy and end up spiraling into the nucleus. The model was called the Suturnian system simply due to the fact that it resembled Saturn's rings. With the rings being the electrons surrounding the planet which would be a concentrated positive charge. -
Albert Einstein
Albert Einstein, a physicist, developed the general theory of relativity which helped us grasp a better view of our world. He was a German physicist and won the Nobel Prize in 1921 for his explanation of the photoelectric effect. He discovered the theory of relativity in 1905 which constituted to his discovery of E=MC squared. This means that the energy of the body (E) is equal to the mass of the body (M) times the speed of light squared. This became the backbone to many scientists theories. -
Ernest Rutherford
Rutherford discovered that the nucleus is charged, and mainly surrounded by empty space. He also discovered that the nucleus is surrounded by tiny electrons and this was the birth of the Rutherford Model. He was able to overturn Thomson's theory in 1911 with his gold foil experiment where he demonstrated that the atom has a tiny but heavy nucleus. -
Period: to
Chien Shiung Wu
Chien Shiung Wu was a Chinese American physicist who helped the field of physics make significant contributions. Wu was so famous that she was recruited for the Manhatten project where she worked on developing a way to split uranium 235 and uranium 238 with diffusion. -
Niels Bohr
In 1913, Bohr proposed a theory for the hydrogen atom which stated that energy is transferred only in well defined quantities. he redesigned the atomic structure model with a single electron moving in prescribed orbits. Each orbit corresponded to a specified energy state. This theory was then extended to other atoms. -
Satyendra Nath Bose
Satyendra worked on quantum physics and relativity and was also able to derive Planck's constant which brought forward a solution that has never been thought of before. He sent his paper to Albert Einstein and ended up working together on a prediction that the state of matter of a dilute gas of bosons which became the Bose-Einstein condensate. -
Werner Heisenberg
Werner Heisenberg was an extraordinary physicist. Being awarded the Nobel Prize at the age of 31, he helped the Germans discover different forms of hydrogen which led to the development of the atomic bomb. -
Louis De Broglie
Louis is most famous for his theory which is that all matter emits some type of wave property. This statement brought him to fame. Up until De Broglie's theory, electrons were seen as only behaving like particles but it was not until De Broglie discovered that each particle emits a wave property that everybody started to change their view of the atom. -
Wolfgang Pauli
Wolfgang Pauli is famous for his principle which states that no two electrons can exist in the same quantum state. In 1925, he used Heisenberg's new matrix theory of quantum mechanics to find the observed spectrum of the hydrogen atom. -
Period: to
Ronald Gillespie
Ronald Gillespie. a chemistry professor at McMaster university, specializes in molecular geometry. He helped pioneer superacids, and furthered our understanding on the factors that influence molecular structure and bonding through valence shell repulsion. -
Erwin Schrödinger
Erwin Schrödinger discovered the quantum mechanical model of the atom. He is also famous for his cat experiment which is sometimes though of as a paradox. He is famous for his development into quantum mechanics. He was dissatisfied with Bohr's diagram because it conflicted with his belief that atomic spectra should be determined by some kind of eigenvalue problem. -
Period: to
Richard Bader
Richard Bader helped extend quantum mechanics to open system. He also wrote his own book on the atoms in molecules. He was a theoretical chemist who specialized in molecular structure and relativity. -
James Chadwick
James Chadwick is famous for discovering the neutron by bombarding a beryllium atom with alpha particles which produced an unknown radiation. Chadwick thought that this was due to particles with a neutral electric charge which soon became known as the neutron. -
Lise Meitner
Lise Meitner is famous for her work with radioactivity. She was looked down upon when working with a male physicist even though she was the one who developed the first theoretical explanation of the fission process uranium goes through. She also found out that nuclear fission produced lots of energy which led to her being called the mother of the atomic bomb. -
Period: to
Robert LeRoy
Robert LeRoy was a brilliant Canadian scientist who worked as a professor at the University of Waterloo. His work was mainly with problems in theoretical and computational chemical physics. Robert was diagnosed with multiple myeloma and was not fazed by it at all. He was always able to have a smile on his face through anything life could throw at him. -
Chien Shiung Wu
Being one of many women that were not directly recognized for their scientific contributions, Chien Shiung Wu was one of the most important factors for extending our knowledge of the atomic theory. In 1945, as she was offered a position at Columbia university where she would learn more about beta decay. This is when the nucleus of one element changes to another. Later on, her discoveries confirmed and greatly contributed to Enrico Fermi's beta decay theory. -
Rober LeRoy
Robert LeRoy started his research on experimental kinetics, but then switched to theoretical / computational physics. He is famous for his development of the Leroy-Bernstein theory and the derivation of the LeRoy radius. He is also the author of many computer programs that help scientists world wide in collecting information from experiments. -
Richard Bader
Richard Bader discovered that electron density is very important in explaining the behavior of atoms in a molecule. His theory states that there are no atomic orbitals in the molecules and was not as accepted, but after he published his book, it became more widely accepted. -
Ronald J. Gillespie
Gillespie studied the shape of molecules and ended up developing the widely used valence shell electron pair repulsion theory. This theory helps scientist describe and or predict the shape of any molecule based on how many electron pairs are in the outer shell.
