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427 BCE
Plato
believing atoms existed by the showing how elements combine to form compounds. -
400 BCE
Democritus
he found out that all bodies are made up of small atoms. he found that atoms are different in size and shape and counld rebound from if they collided together. -
384 BCE
Aristotle
Matter was constructed out of atoms. -
Robert Boyle
If the volume of gas decreases the pressure increases. 'corpuscular theory'. this explains why gasses are made up of tiny particles. -
Lavoisier
Total mass in products and reactants in chemical reaction the chemical reactions are all the same. The law of conservation mass. -
the Alchemists
They came up with the foundation of periodic table. Fire, earth, wind, and water are they elements they broke down. -
John Dalton
All matter is comprised of tiny, definite particles called atoms.
Atoms are indivisible and indestructible.
All atoms of a particular element share identical properties, including weight.
Atoms of different elements contain different mass. -
Demetri Mendeleev
he arranged all the elements to atomic weight. He found out that the properties repeated. -
J.J. Thomson
all atoms contain tiny negatively charged subatomic particles or electrons. he discovered the electron. -
The curies
conducted a experiment of uranium rays. They discovered the radioactive elements which are polonium and radium. -
Planck's Quantum Theory of light
the energy of light is proportional to the frequency. the energy of each quantum is equal to the frequency of the radiation multiplied by a universal constant. -
Photoelectric Effect
Light has particle like activity. The electrons that are projected determine wave length. -
Albert Einstein
any liquid is made up of molecules. calculated that a force of a pollen is a grain floating in water. -
Robert Millikan
he discovered the charge of a electron. by the falling drop method -
Earnest Rutherford
the atom is a small positively charged nucleus with with negative charged electrons. A beam was aimed through a piece of gold foil and most of the particles passed through but some came backwards. this showed that the atom has many empty space. -
Neil's Bohr
The theory of hydrogen atom. electrons move around the nucleus but in order the have a set size and order. -
Henry G.J. Mosely
self-built equipment to prove that every element's identity is uniquely determined by the number of protons it has. -
Schrodinger Equation
in 1926 Erwin Schrödinger formulated a wave equation that accurately calculated the energy levels of electrons in atoms. -
Werner Heisenberg
He discovered the uncertainty principle. This means that a particles position and momentum can not be known. -
James Chadwick
He discovered the neutron. A neutron is a particle with no electric charge.