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448 BCE
plato
Plato's most famous work is the Republic, which details a wise society run by a philosopher. He is also famous for his dialogues -
400 BCE
democritus
He developed the concept of the 'atom', Greek for 'indivisible' -
367 BCE
Aristotle
. He made pioneering contributions to all fields of philosophy and science, he invented the field of formal logic, and he identified the various scientific disciplines and explored their relationships to each other. -
330 BCE
Solar system model
The answer took a while for astronomers to figure out, leading to a debate between what is known as the geocentric (Earth-centered) model and the heliocentric (Sun-centered model) -
robert boyle
discovered that the volume of a gas decreases with increasing pressure and vice versa -
the alchemists
Alchemists laid the groundwork for many chemical processes, such as the refining of ores, the production of gunpowder, the manufacture of glass and ceramics, leather tanning, and the production of inks, dyes, and paints -
Lavoisier
meticulous experimenter, revolutionized chemistry. He established the law of conservation of mass, determined that combustion and respiration are caused by chemical reactions with what he named “oxygen,” and helped systematize chemical nomenclature, among many other accomplishments. -
John Dalton
an English chemist, physicist, and meteorologist, best known for introducing the atomic theory into chemistry and for his work on human optics -
Solid Sphere of "Billiard Ball' Model
The Solid Sphere model is an atomic model proposed by John Dalton in 1803 stating that all objects are made of particles called atoms, and that they are solid spheres that cannot be divided further into smaller particles. This is similar to the model made by the Greeks in the fifth century BCE. -
Dmitri Mendeleev
Russian chemist Dmitri Mendeleev jotted down the symbols for the chemical elements, putting them in order according to their atomic weights and inventing the periodic table -
Photoelectric effect
photoelectric effect, phenomenon in which electrically charged particles are released from or within a material when it absorbs electromagnetic radiation -
"Plum Pudding" model
To explain the two types of static electricity, he suggested that the atom consisted of positive 'dough' with a lot of negative electrons stuck in it. -
JJ Thomas
British physicist J.J. Thomson announced his discovery that atoms were made up of smaller components. This finding revolutionized the way scientists thought about the atom and had major ramifications for the field of physics -
Plank Quantum Theory of Light
Planck postulated that the energy of light is proportional to the frequency -
Robert Millikan
His earliest major success was the accurate determination of the charge carried by an electron, using the elegant “falling-drop method”; he also proved that this quantity was a constant for all electrons -
the curies
Pierre Curie first discovered the radioactive elements polonium and radium -
ernest rutherford
He discovered that there are two types of radiation, alpha and beta particles, coming from uranium. He found that the atom consists mostly of empty space, with its mass concentrated in a central positively charged nucleus. -
neil bohr
In 1913, Bohr launched the modern era of atomic physics when he combined the quantum theory of Max Planck with the new nuclear atom of Ernest Rutherford -
Henry GJ Mosely
while working at the University of Manchester, he observed and measured the X-ray spectra of various chemical elements using diffraction in crystals. Through this, he discovered a systematic relation between wave- length and atomic number. This discovery is now known as Moseley's Law -
albert einstein
Einstein is best known for developing the theory of relativity, but he also made important contributions to the development of the theory of quantum mechanics -
werner heisenberg
Werner Heisenberg contributed to atomic theory through formulating quantum mechanics in terms of matrices and in discovering the uncertainty principle, which states that a particle's position and momentum cannot both be known exactly. -
Schrodinger Equation
Schrodinger equation gives us a detailed account of the form of the wave functions or probability waves that control the motion of some smaller particles -
Electron cloud Model
An electron cloud represents the area around an atom's nucleus where electrons are most likely to be found. ... The cloud is darkest at the nucleus and lighter farther away, representing that electrons are more likely to be found closer to the nucleus than away from it -
James Chadwick
made a fundamental discovery in the domain of nuclear science: he proved the existence of neutrons – elementary particles devoid of any electrical charge.
