-
370 BCE
Democritus
Democritus, known in antiquity as the 'laughing philosopher' because of his emphasis on the value of 'cheerfulness,' was one of the two founders of ancient atomist theory. He elaborated a system originated by his teacher Leucippus into a materialist account of the natural world. -
300 BCE
Plato
PLATO (Package for Linear-combination of Atomic Orbitals) is a suite of programs for electronic structure calculations. It receives its name from the choice of basis set (numeric atomic orbitals) used to expand the electronic wavefunctions. Plato introduced the atomic theory which ideal geometric forms serve as atoms, according to which atoms broke down mathematically into triangles, such that the form elements had the following shape: fire (tetrahedron), air (octahedron), water (icosahedron). -
300 BCE
Aristotle
Aristotle thought that proper mixing could occur when substances of comparable amounts are brought together to yield other substances called 'compounds. ' Accordingly, the substances we typically encounter are compounds, and all compounds have the feature that there are some ingredients from which they could be made. -
Lavoisier
matter was neither created nor destroyed in chemical reactions, and in his experiments he sought to demonstrate that this belief was not violated -
John Dalton
John Dalton was an English chemist, physicist and meteorologist. He is best known for introducing the atomic theory into chemistry, and for his research into color blindness, which he had. Color blindness is known as Daltonism in several languages, being named after him. -
The Alchemists
The alchemists believed that all metals were formed from two principles — mercury and sulfur. The mercury, with its essential property of fluidity and fusibility, gave rise to the malleability of metals. The Sulphur, with its essential property of combustibility, contributed body and calcination(Rusting) -
Newlands law of octaves
If the chemical elements are arranged according to increasing atomic weight, those with similar physical and chemical properties occur after each interval of seven elements. -
Mendeleev's Pd. table
In his periodic table, Mendeleev arranged elements in rows by increasing atomic mass. Within a row, elements with lower atomic masses were on the left. Mendeleev started a new row every time the chemical properties of the elements repeated. Thus, all the elements in a column had similar properties. -
Photoelectric effect
photoelectric effect, phenomenon in which electrically charged particles are released from or within a material when it absorbs electromagnetic radiation. The effect is often defined as the ejection of electrons from a metal plate when light falls on it. -
Discovery of Radioactivity
Henri Becquerel Discovers Radioactivity. In one of the most well-known accidental discoveries in the history of physics, on an overcast day in March 1896, French physicist Henri Becquerel opened a drawer and discovered spontaneous radioactivity. -
Discovery of the Electron
Thomson discovered the electron by experimenting with a Crookes, or cathode ray, tube. He demonstrated that cathode rays were negatively charged. In addition, he also studied positively charged particles in neon gas. -
Planck's Quantum Theory of light
Specifically, Planck's quantum theory of fussy light tells us that light bulb filaments should be heated to a temperature of about 3,200 Kelvin to ensure that most of the energy is emitted as visible waves. Much hotter, and we'd start tanning from the ultraviolet light. -
Plum Pudding Model
The plum pudding model is defined by electrons surrounded by a volume of positive charge, like negatively-charged “plums” embedded in a positively-charged “pudding” as suggested in the name. -
Rutherford's Gold Foil Experiment
The Geiger–Marsden experiments were a landmark series of experiments by which scientists learned that every atom has a nucleus where all of its positive charge and most of its mass is concentrated. They deduced this after measuring how an alpha particle beam is scattered when it strikes a thin metal foil. -
Robert Millikan
Robert Millikan was a physicist who discovered the elementary charge of an electron using the oil-drop experiment. -
charge of the electron
Millikan Oil Drop Experiment -
Mosley's Atomic number
Moseley published a paper in which he concluded that the atomic number is the number of positive charges in the atomic nucleus. He also stated that there were three unknown elements, with atomic numbers 43, 61, and 75, between aluminum and gold. -
Bohr's planetary model
According to the Bohr model, often referred to as a planetary model, the electrons encircle the nucleus of the atom in specific allowable paths called orbits. -
discovery of proton
The proton was discovered by Ernest Rutherford in the early 1900's. During this period, his research resulted in a nuclear reaction which led to the first 'splitting' of the atom, where he discovered protons. He named his discovery “protons” based on the Greek word “protos” which means first. -
Schrodinger Equation
The Schrödinger equation is a linear partial differential equation that governs the wave function of a quantum-mechanical system. It is a key result in quantum mechanics -
Heisenberg uncertainty principle
In quantum mechanics, the uncertainty principle is any of a variety of mathematical inequalities asserting a fundamental limit to the accuracy with which the values for certain pairs of physical quantities of a particle, such as position, x, and momentum, p, can be predicted from initial conditions. -
Discovery of Neutron
The discovery of the Neutron is its properties was central to the extraordinary developments in atomic physics in the first half of the 20th century. Early in the century, Ernest Rutherford developed a crude model of the atom,[1]: 188 [2] based on the gold foil experiment of Hans Geiger and Ernest Marsden. Atomic number had been identified as the charge on the nucleus.