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369 BCE
Democritus
Democritus was an ancient Greek philosopher. He is best known for developing the idea of "atomos" indivisible particles. He believed everything in the universe was made of these atoms and void. A visionary in his time. His theories were way ahead of their time. He even thought atoms had different shapes and sizes. -
347 BCE
Plato
What is Plato known for? Plato's most famous work is the Republic, which details a wise society run by a philosopher. He is also famous for his dialogues (early, middle, and late), which showcase his metaphysical theory of forms—something else he is well known for. -
322 BCE
Aristotle
Aristotle is a towering figure in ancient Greek philosophy, who made important contributions to logic, criticism, rhetoric, physics, biology, psychology, mathematics, metaphysics, ethics, and politics. He was a student of Plato for twenty years but is famous for rejecting Plato’s theory of forms. He was more empirically minded than both Plato and Plato’s teacher. -
16 BCE
The Alchemists
Alchemists were like early chemists, trying to turn metals into gold and find immortality potions. Their work laid foundations for modern chemistry. They invented tools and techniques we still use. They studied elements and substances seeking to understand the universe's mysteries. -
John Dalton
Soon after moving to Manchester, Dalton joined the Literary & Philosophical Society. It was a discussion group set up to share scientific ideas at a time when science had yet to become a profession. Though sometimes criticised for the quality of his experiments, Dalton was an enthusiastic investigator who worked late most evenings. He read over 100 papers to the Society. Through his experimentation, Dalto formulated a new atomic theory to explain chemical reactions -
John Dalton
John Dalton was an English chemist, physicist, and meteorologist, best known for introducing the atomic theory into chemistry and for his work on human optics. The first part of his theory states that all matter is made of atoms, which are indivisible. The second part of the theory says all atoms of a given element are identical in mass and properties. The third part says compounds are combinations of two or more different types of atoms. -
Mendeleev's Pd. Table
it organizes elements by atomic weight and properties. Mendeleev noticed patterns, so he arranged elements into rows and columns. this predicted new elements too. He left gaps for undiscovered elements and predicted their properties. it helped science advance a lot. -
Photoelectric Effect
The photoelectric effect is a phenomenon in which electrons are ejected from the surface of a metal when light is incident on it. These ejected electrons are called photoelectrons. It is important to note that the emission of photoelectrons and the kinetic energy of the ejected photoelectrons is dependent on the frequency of the light that is incident on the metal’s surface. -
Discovery of 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. Becquerel initially believed his rays were similar to x-rays, but his further experiments showed that unlike x-rays, which are neutral, his rays could be deflected by electric or magnetic fields. -
Planck's Quantum Theory of Light
He proposed that energy is quantized, meaning it comes in discrete amounts. It led to the idea that particles can also behave like waves. Planck's theory suggests light is made of packets of energy called "quanta" Revolutionary. -
Robert Millikan
Robert figured out the charge of an electron through his oil-drop experiment. His experiment was complex, but he balanced gravity with electric force on tiny oil drops to find the electron's charge. He won the Nobel Prize in Physics in 1923 for his work. -
Plum Pudding Model
Soon after the discovery of the electron, before the discovery of the atomic nucleus, the model tried to account for two properties of atoms then known: that electrons are negatively charged subatomic particles and that atoms have no net electric charge. The plum pudding model has electrons surrounded by a volume of positive charge, like negatively charged "plums" embedded in a positively charged "pudding". -
Rutherford's Gold Foil Experiment
In 1911, Rutherford and coworkers Hans Geiger and Ernest Marsden initiated a series of groundbreaking experiments that would completely change the accepted model of the atom. They bombarded very thin sheets of gold foil with fast moving alpha particles. Alpha particles, a type of natural radioactive particle, are positively charged particles with a mass about four times that of a hydrogen atom. -
Mosley's Atomic Numbers
Henry Moseley discovered that every element's identity is uniquely determined by its number of protons. Before Moseley, elements were arranged by atomic weight. His work in 1913 changed everything. He found that the X-ray frequencies of elements corresponded to atomic numbers, not weight. -
Bohr's Planetary Model
Bohr's Model is just like the solar system, with a sun as the center like the nucleus of the atom and the planets locked in defined orbits like the electrons locked in orbits around the nucleus. In July of 1913, Niels Bohr published the first of a series of three papers introducing this model of the atom, which became known simply as the Bohr atom.Jul 12, 2013 -
Discovery of the Proton
The discovery of the proton is from Ernest Rutherford, who proved that the nucleus of the hydrogen atom is present in the nuclei of all other atoms in the year 1917. Based on the conclusions drawn from the gold-foil experiment, Rutherford is also credited with the discovery of the atomic nucleus. -
Schrodinger Equation
Its a key equation in quantum mechanics, showing how quantum systems change over time. It uses wave functions to predict probability distributions of a particle's location. Its also used to calculate energies of stable states, like atoms and molecules. -
Heisenberg Uncertainty Principle
Uncertainty principle, also called Heisenberg uncertainty principle or indeterminacy principle, statement, articulated (1927) 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. The very concepts of exact position and exact velocity together, in fact, have no meaning in nature. -
Discovery of the Nutron
In 1932, the physicist James Chadwick conducted an experiment in which he bombarded Beryllium with alpha particles from the natural radioactive decay of Polonium. The resulting radiation showed high penetration through a lead shield, which could not be explained via the particles known at that time.With the postulate of an uncharged (neutral) particle, of about the same weight as a proton, however, Chadwick's interpretation problems disappeared quite naturally.