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420 BCE
Democritus
Democritus claims everything is made up of smallest particles and named then atoms. -
400 BCE
Plato
Plato claims that everything is made up of tiny geometrical shapes containing the elements of air, water, earth, and fire. -
300 BCE
Aristotle
Aristotle states everything is made of either water, air, earth, or fire and that a void between atoms could exist. -
100
Alchemists
Alchemists believed that they could make base metal turn into gold using similar substances using the right ratios paving the way for common chemistry. -
Robert Boyle
Boyle finds that everything is made of tiny particles and calls them corpuscles. Now known as the atom. -
John Dalton
Dalton makes the Atomic Theory stating that everything is made up of invisible and indestructible small things called atoms. -
Newland's Law of Octaves
Newland claimed that when the elements are arranged in atomic mass order, there will be similarities between the first interval and eighth interval. -
Mendeleev's pd. table
Mendeleev creates the common periodic table. -
Photoelectric effect
Hertz experiments with charged particles on metal plates to find that particles may be electrically charged. -
Robert Millikan
Millikan discovers the charge of a single electron. -
Discovery of radioactivity
Becquerel discovers radioactivity when experimenting how uranium salts are affected by light. -
Planck's quantum theory of light
Planck states that light is emitted as a continuous wave in packets of energy called photons. -
Plum pudding model
Thomson experiments show that all atoms have subatomic particles called electrons with negative charges. -
Rutherford's gold foil experiment
Rutherford finds out that atoms are mostly empty space with a positively charged nucleus. -
Bohr's planetary model
Bohr discovered a model that shows where and how the electrons orbit the nucleus in their circular paths. -
Mosley's atomic numbers
Mosley gave elements all their number that represents their order and the number of positive protons. -
Discovery of the Proton
Rutherford discovered the proton when he experimented with nitrogen atoms and alpha particles. -
Schrodinger equation
Schrodinger creates a linear equation that shows a wave function of non-realistic quantum-mechanical system. -
Heisenberg uncertainty principle
Heisenberg finds that we cannot find the exact speed or position of the photons or electrons. Whenever you get closer to one's answer, you get further from the other answer. -
Discovery of the neutron
Chadwick uses beryllium and alpha particles to find there is a neutral particle in the atom similar to the proton.