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460 BCE
Democritus
Greek philosopher and scientist. He contributed to the theory of atomism,by suggesting that all matter consisted of tiny, indivisible particles.They believed that everything is made of tiny things that never get deleted, they can only be moved or changed. He is also known as 'the Laughing Philosopher' as he was often cheerful while at work. -
384 BCE
Aristotle
Aristotle was a student of Plato and he is a scientist and philosopher, he was the teacher of Alexander the Great. He founded his own school, and spent most of his time studying and teaching there. He made contributions to logic, metaphysics, physics, biology, botany, ethics, politics, agriculture, medicine, dance and theatre. Aristotle did not believe in the atomic theory. -
Apr 24, 1494
George Bauer
was a German mineralogist and metallurgist. He is known as "the father of mineralogy." He is best known for his book De Re Metallica.The hot rock was quenched with water, and the thermal shock weakened it enough for easy removal. It was a dangerous method when used underground, and was made redundant by explosives. -
Robert Boyle
He is best known for Boyle's law, which describes the inversely proportional relationship between the absolute pressure and volume of a gas, if the temperature is kept constant within a closed system. He disagreed with Aristotle. Robert Boyle wrote a book, he overturned Aristotle's conception of the four elements and replaced it with the modern idea of an element, namely that an element is a substance that cannot be separated into simpler components by chemical methods. -
Robert Millikan
American physicist Robert Millikan's oil drop experiment helped to quantify the charge of an electron, which contributed greatly to our understanding of the structure of the atom and atomic theory. He also determined that there was a smallest 'unit' charge, or that charge is 'quantized'. -
Antoine Lavoisier
Lavoisier is most noted for his discovery of the role oxygen plays in combustion. He recognized and named oxygen and hydrogen and opposed the phlogiston theory. He proposed the Combustion Theory which was based on sound mass measurements. Antoine Laurent, French chemist who founded modern chemistry. His work was crucial in a period of discovery that is now known as the Chemical Revolution, or even the First Chemical Revolution. -
Joseph Proust
He first published his Law of Definite Proportions in 1794. This law states that a compound is composed of exact proportions of elements by mass regardless of how the compound was created. Joseph Louis Proust was a French chemist. -
John Dalton
Dalton's atomic theory remains valid in modern chemical thought. All matter is made of atoms. Atoms are indivisible and indestructible. Compounds are formed by a combination of two or more different kinds of atoms. Dalton's atomic theory proposed that all matter was composed of atoms, indivisible and indestructible building blocks. While all atoms of an element were identical, different elements had atoms of differing size and mass. -
Amedeo Avogadro
Amedeo Avogadro is best known for his hypothesis that equal volumes of different gases contain an equal number of molecules, provided they are at the same temperature and pressure. His hypothesis was rejected by other scientists. It only gained acceptance after his death. He was a Italian mathematical physicist. -
Joseph Gay-Lussac
Gay-Lussac's Law shows the relationship between the Temperature and Pressure of a gas. At a fixed volume, the temperature and pressure of a gas are directly proportional to each other. Joseph Louis Proust was a French chemist. -
Henri Becquerel
He realized that some invisible radiation had been emitted from the uranium. French physicist who discovered radioactivity through his investigations of uranium and other substances. -
J.J. Thomas
J.J. 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. He discovered protons with the experiments he did with cathode rays which would knock electrons of atoms and attract them to a positively charged electrode. -
Max Planck
Planck's law describes the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium at a given temperature T. The law is named after Max Planck, who proposed it in 1900. It is a pioneering result of modern physics and quantum theory. The Planck constant links the amount of energy a photon carries with the frequency of its electromagnetic wave. -
Ernest Rutherford
he was the first to discover that atoms have a small charged nucleus surrounded by largely empty space, and are circled by tiny electrons, which became known as the Rutherford model of the atom. Rutherford overturned Thomson's model, his well-known gold foil experiment in which he demonstrated that the atom has a tiny and heavy nucleus. Rutherford designed an experiment to use the alpha particles emitted by a radioactive element as probes to the unseen world of atomic structure. -
Niels Bohr
Bohr was the first to discover that electrons travel in separate orbits around the nucleus and that the number of electrons in the outer orbit determines the properties of an element. Niels Bohr proposed a theory for the hydrogen atom based on quantum theory that energy is transferred only in certain well defined quantities. Electrons should move around the nucleus but only in prescribed orbits. When jumping from one orbit to another with lower energy, a light quantum is emitted. -
Erwin Schrodinger
Erwin Schrödinger, an Austrian physicist, took the Bohr atom model one step further. Schrödinger used mathematical equations to describe the likelihood of finding an electron in a certain position. This atomic model is known as the quantum mechanical model of the atom.developed an “Electron Cloud Model” in 1926. It consisted of a dense nucleus surrounded by a cloud of electrons at various levels in orbitals. -
Louis de Broglie
The Born rule in Broglie–Bohm theory is not a basic law. Rather, in this theory, the link between the probability density and the wave function has the status of a hypothesis, called the quantum equilibrium hypothesis, which is additional to the basic principles governing the wave function. -
Werner Heisenberg
Heisenberg is best known for his uncertainty principle and theory of quantum mechanics.For this theory and the applications of it which resulted especially in the discovery of allotropic forms of hydrogen.Uncertainty principle, also called Heisenberg uncertainty principle or indeterminacy principle, statement, articulated by the German physicist Werner Heisenberg, that the position and the velocity of an object cannot both be measured exactly, at the same time, even in theory.
