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460 BCE
Lucippus & Democritus
Started the idea of everything is composed of tiny particles. If you cut something in half enough times, you will eventually get what is uncuttable anymore. They called the that particle the "A Tomos", meaning uncuttable or indivisible. This theory was rejected by almost all at the time because its atheistic nature. -
200 BCE
Alchemists
Alchemists studied the teaching of Aristotle, who believed in the four elements and a divine force. Their goal was to turn objects into gold, therefore increase its value. Although their methods was limited and unsuccessful, their left tools such as flasks, reaction vessels, and other lab equipment that set the stage for later development of atomic theory. Their work also heavily relied on distillation, calcination, etc., giving later scientists samples of chemistry reactions. -
John Dalton
John Dalton's theory recognized the different types of atoms. From his studies of gases, he concluded that the atoms of the same element will have the same mass, different elements will have different mass. -
Joseph John Thomson
Using the cathode ray, gas-filled tube with electros at each end and emits light when a current passes through them, he was able to use the calculation of temperature and their curves with magnet, Joseph John Thomson theorized tiny particles with mass 1000 times lighter than the hydrogen atoms with negative charges exist. He named these particles corpuscles, what are known as electrons today. -
Albert Einstein
Before 1905 and Einstein, Dalton's theory of this atom was regarded by physics as a convenient hypothesis to explain matter, there were people who did not believe in the actual existence of atom. But Einstein came along and proved its existence in practice of small particles moving freely in water a.k.a the Brownian Motion. He also proposed that light, a phenomenon that was also being associated with waves can be particles to as photons. This will affect future scientist Niels Bohr. -
Ernest Rutherford
Thomson's model envisions an atom with electrons floating around everywhere. But Ernest Rutherford used a thin gold foil and exposed it with radium's decaying positive alpha particles to see how the particles reflect. And some of those particles pass through the foil, but a tiny amount strangely got reflected backwards. Which means there could be a concentrated core that has a positive charge in all atoms, i.e. a nucleus. His work also extended to nuclear decay and radiation physics. -
Niels Bohr
Two years after Rutherford published the finding of nucleus, Niels Bohr joined his research. By repeating Rutherford's experiment and calculating the deflection of the alpha particles, Bohr was able to find the orbits of the electrons. His model was called the planetary model due to its resemblance with the solar system. He later perfected this theory with Max Planck's Quantum Theory to theorize the "jumping" of the electrons between orbits and the emission of photon. -
Max Planck
By observing the color change in iron during raise in temperature, Max Planck hypothesize that atoms can emit or absorb energy to shift the electrons in and out of their orbit and meanwhile release a photon. A red photon release is associated with low energy, and a violet photon is the effect of a higher energy. His theory influenced Bohr and let the create an improved theory. -
Louis de Brogile
He proposed the theory that small particles at the electron scale has both the property of a wave and a particle. -
Erwin Schrödinger
Based on Louis de Broglie's theory, Schrödinger use math to realize a wavefunction to describe the behavior of electrons as waves. This introduced the wave-particle duality theory. Since it describe all the possible states where an electron might be, Schrödinger's wavefunction helped built the orbital cloud model of atom that Heisenberg will later propose. -
Wolfgang Pauli
Wolfgang Pauli is most famous for his Pauli exclusion principle. The principle stated that there cannot be two identical electrons that occupy in the same quantum state within an atom. Which means that if the first three number of the orbital address of an electron is given, there can only be one 1/2 spinning electron and one -1/2 spinning electron. In other words, no electron has the exact same address as any other electron in the atom. -
Werner Heisenberg
Because the electrons are so small, when light touches them, they change course. This made it impossible for human to detect either their exact location or their momentum. This created the uncertainty principle that opposes the orbital model that Bohr created. Heisenberg influenced model imagined clouds surrounding the nucleus that represents where the electrons might be found. These clouds are called the orbitals, they can be classified into s, p, d, f, etc. -
James Chadwick
James Chadwick studied the experiment made by Walter Bothe and used beryllium and its radiation to bombard other elements with alpha particles. While studying the results, he realized that there are neutrally charged particles emitting radiation with mass same as the proton. Therefore he concluded a similar particle that exist in nucleus with protons, called neutrons. -
Hideki Yukawa
Hideki Yukawa is a Japanese physicist who predicted and detected pi meson. This particle strengthened our knowledge of the strong nuclear force. -
Maria Goeppert Mayer
Maria Goeppert Mayer is a woman physicist who came up with the atomic shell theory. First developed in the 1950s, Mayer used the Pauli exclusion principle to model the electron orbitals of an atom. Her atom shell model combined energy level and 3D geometry to map possible locations of electrons orbitals. Her work is acknowledged and received a Nobel Prize in 1963 -
Leo Esaki
Leo Esaki is a Japanese physicist who studied the property of metal conductor. He used the quantum mechanics of atomic structure to create a better superconductor. A semiconductor that have negative resistance, is named Esaki diode. -
Richard E. Taylor
Richard E. Taylor was a Canadian physicist, he worked with Jerome I. Friedman and Henry W. Kendall and discovered the structure of protons. More importantly, they discovered what might be inside the proton. His work first opened the study of particles like quarks, and different types of quarks that functioned in protons and neutrons that brought the atom together -
Arthur B. MacDonald
Arthur B. MacDonald is a Canadian physicist who with Takaaki Kajita proved the mass and properties of neutrinos. This gave us more insights on the subatomic particle. His research was completed in the SNOLAB, based in Sudbury, Ontario. -
Donna Stickland
Donna Stickland is a woman Canadian physicist. Her work with high intensity laser made moving objects using light possible. This used the mass in photon and energy ejection of atom. A groundbreaking invention not only for atomics properties, but also the real world technology. Her work was done in University of Waterloo, Ontario
