-
500 BCE
The Alchemists
The Alchemists broke down the composition of the 4 basic elements. These 4 elements turned into the Periodic Table of Elements. -
400 BCE
Democritus
He discovered that everything is composed of atoms. He also discovered that atoms are always in motion and will always be. Also he believes that there is an infinite amount of atoms and the types of atoms. -
384 BCE
Aristotle
He did not believe in the atomic theory. He thought instead that all materials were made of the four known elements at that time. Earth, Fire, Water and Air. -
47 BCE
Plato
Plato created the atomic theory. This theory includes that atoms broke down into geometric shapes. And the elements at the time fire, air, water, and earth had shapes. -
Robert Boyle
He proposed that the elements were composed of many different sizes and variations of what he called corpuscles. He proposed that these corpuscles could organize themselves and create different chemical substances. -
Lavoisier
He learned that oxygen was a key element in reactions. he also developed the modern naming system for chemical substances. -
John Dalton
He brought the law of conservation of mass and the law ( mass cannot be created or destroyed) and the law of definite proportions (elements that are compounds will always have the same ratio) and explained them using the idea of atoms. He explained that all matter is made up of atoms. -
Dmitri Mendeleev
He created the first Periodic Table of Elements by ordering elements by atomic weight. -
Ernest Rutherford
He discovered that there are to different types of radioactivity. He also found the nucleus, protons and neutrons of the atom witch lead him into making a new model. -
The curies
Marie Curie discovered that the amount of radiation in an element doesn't depend on how many atoms are in the element. The amount of radiation depends on the interior of the atom itself. -
J.J Thomson
He is credited for finding that there are negatively charged partials in atoms, these are called electrons. He also created a new model of what an atom looks like -
Albert Einstein
He proved in math that atoms are real. This equation E= Mc2 helped create the atomic bomb. -
Robert Millikan
He discovered the size of the charge of an electron. He also found the smallest unit of charge. -
Henry G. J. Mosley
He discovered a relationship between a x-ray's wave length and its atomic number. He also discovered that there are 3 missing elements between aluminum and gold. -
Neiles Bohr
He proposed a theory based on the quantum theory that electrons travel in a circular pattern that orbits around the center of the atom. -
Werner Heisenberg
He contributed to the atomic theory by discovering the uncertainty principal that states that a partial's position and momentum cannot be known exactly.
