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428 BCE
Plato
Greek philosopher born in Athens. Most famous work is the Republic and for his dialogues. -
400 BCE
Democritus
Democritus was a central figure in the development of the atomic theory of the universe. He theorized that all material bodies are made up of indivisibly small "atoms." -
384 BCE
Aristotle
He was taught by Plato. Founder of a school. -
Lavoisir
Discovery of the role oxygen plays in combustion. He recognized and named oxygen in 1778 and hydrogen in 1783. -
John Dalton
Dalton's atomic theory suggested that all matter was comprised of indivisible and indestructible atoms with distinct masses and properties, the combination of which the physical nature of their constituent elements. -
Newland's 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
Published a period table and arranged the elements known at the tome in order of relative atomic mass. -
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
Herni Becquerel discovered radioactivity. In one of the most well-known accidental discoveries in the history of physics, on an overcast day, French physicist Becquerel opened a drawer and discovered spontaneous radioactivity. -
Discovery of the electron
Scientists searched cathode rays for the carrier of the electrical propertied in matter. Their work culminated in the discovery by English physicist J.J Thomson. -
Charge of the Electron
Electron, lightest stable subatomic particle known. It carries a negative charge. -
Discovery of the proton
The proton was discovered by Ernest Rutherford in the early 1900's. During this period his research 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 work "protos" which means first. -
Plum Pudding Model
The plum pudding model is a historical scientific model of the atom. 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" (hence the name). -
Planck's Quantum Theory of Light
Planck's quantum of 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. -
Rutherford's Gold Foil Experiment
A piece of gold foil was hit with alpha particles, which have a positive charge. Most alpha particles went right through. This showed that the gold atoms were mostly empty space. -
Bohr's Planetary Model
The electrons encircle the nucleus of the atom in specific allowable paths called orbits. When the electron is in one of these orbits, its energy is fixed. -
Robert Millikan
Physicist who discovered the elementary charge of an electron using the oil-drip experiment. -
Moseley's Atomic Numbers
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. -
Heisenberg Uncertainty Principle
The uncertainty principle states that we cannot know both the position and speed of a particle, such as a photon or electron, with perfect accuracy; the more we nail down the particle's position, the less we know about its speed and vice. -
Discovery of the Neutron
German nuclear physicists observed that a penetrating form of radiation was produced when the alpha particles emitted by polonium was incident in relatively light elements such as lithium, beryllium, and boron. -
Schrodinger Equation
Linear partial differential equation that governs the wave function of quantum-mechanical system. It is a key result in quantum mechanics, and its discovery was a significant landmark in the development of the subject. -
The Alchemists
A story about base metals that turn into gold when in reality they cannot be.