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440 BCE
Plato
Plato was a Geek philosopher. He discovered the atomic theory where geometric from serve as atoms. -
400 BCE
Democritus
Democritus believed that atoms were uniformed, hard, solid, indestructible, incompressible, and that they moved in infinite numbers through empty space until they stopped. -
384 BCE
Aristotle
Aristotle was a Greek philosopher. He introduced the four bodies; fire, water, air, and earth and said that these bodies produced every substance on Earth, but that theory was proven wrong later. -
Lavoisier
Lavoiser is most known for his discovery of oxygen and its role in combustion. He also helped create the metric system, helped reform the chemical nomenclature, wrote the first list of elements, and discovered that mass always remains the same. helped construct the metric system, wrote the first extensive list of elements, and helped to reform chemical nomeclature -
The Alchemists
Alchemists believed that all metals were formed from the two principles mercury and sulfur. -
John Dalton
John Dalton was an English chemist, physicist and meteorologist. He introduced the atomic theory, which states that all matter is composed of atoms. -
Newland's Law of Octaves
If arranged according to increase in atomic weight, the chemical elements with similar physical and chemical properties occur after each interval of seven elements. Create by chemist J.A.R. Newlands in 1865 -
Mendeleev’s Pd. Table
Mendeleev arranged the elements into organized groups to the elements, after realizing the properties of an element and their atomic mass were related. -
Photoelectric Effect
Discovered by Heinrich Rudolf Hertz. When electrically charged particles are released from a material when it absorbs electromagnetic radiation. -
radioactivity
Discovered by Henri Becquerel. This was an accidental discovery. He put uranium crystals and photographic plates, from different experiment, into drawer and when he opened it later, it had become radioactive. -
the discovery of the electron
Discovered by J.J. Thomson. While experimenting with cathode ray tubes, Thomson discovered that all atoms contain electrons, tiny negatively charged subatomic particles. -
The proton
Ernest Rutherford discovered the proton. During his research, he created a nuclear reaction which led to the splitting of the atom, which led him to his discoverv of protons. -
Planck’s Quantum of Light
The theory that ight bulb filaments should be heated to a temperature of about 3,200 kelvin to make sure that most of the energy is emitted into visible waves. -
Plum pudding model
Discovered by J.J. Thompson. The model shows the electrons as negatively charged particles in a sea off positive charge. The structure of the model resembles the English dessert, plum pudding. -
Rutherford's gold foil experiment
Alpha particles, which are negative, hit a piece of gold foil. Most of the particles went right through, showing that the gold atoms were mostly empty space. -
Robert Millikan
Robert Millikan was a physicist who is most known for discovering the elementary charge of an electron using the oil-drip method. -
Bohr's planetary model
created by Niels Bhor. the model shows the electrons orbiting around the nucleus of an atom. This model can also be called the planetary model of an atom. -
Mosley’s Atomic Numbers
Mosley discovered that the atomic number is positive charges in the atomic nucleus. He discovered the relation between atomic numbers nd wave-length. -
charge of electron
Discovered by Robert Millikan he disovered the charge of the electron by using the oil-drop experiment -
Schrodinger Equation
Discovered by Erwin Schrödinger. An equation that is a linear differential equation that governs the wave function of a quantum-mechanical system. -
Heisenberg Uncertainty Principle
This principle states that We cannot know both the exact speed and the position of a particle -
Discovery of the neutron
Discovered by James Chadwick. He discovered that the core of an atom contained uncharged particles, neutrons.