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Period: 550 BCE to
Atomic Timeline
The Evolution of the Atom -
500 BCE
The Alchemists
The Alchemists came up with several new elements that they formed from the basic elements of their time period, earth, fire, wind, and water. These new elements would eventually lead to the beginning of the periodic table. -
427 BCE
Plato
Plato believed atoms came from the basic build of five solid shapes, triangles, squares, pentagons, hexagons, and octagons. -
400 BCE
Democritus
Democritus developed the idea of the atom. He defined an atom as tiny particles that are always in motion. -
Robert Boyle
Robert Boyle was the first person to define the word element. He linked chemical changes to the rearrangement of particles within matter. -
Antone Lavoisier
Antone discovered that mass stays the same in a chemical reaction because the total mass of substances does not change. -
Billiard Ball Model
The Billiard Ball Model was made by John Dalton to show his theory of atoms being the smallest particles of matter by creating them into solid wooden spheres. -
John Dalton
Dalton created a theory stating that atoms make up all matter. -
Amedeo Avogadro
Amedeo Avogadro learned that if different gases are at the same temperature and pressure and have the same volumes then they will contain an equal number of atoms. -
Dmitri Mendeleev
Dmitri Mendeleev is known for inventing the periodic table of elements. He put all chemical elements down in one place as symbols and ordered the elements based on their atomic weights. -
JJ Thompson
Thompson discovered the electron and built a model to show the structure of an atom. -
Plum Pudding Model
The Plum Pudding Model was proposed by Joseph John Thompson and was a model of an atom that showed the positive and negative charge of an atom. -
Marie and Pierre Curie
The Curies discovered the two chemical elements, polonium, and radium. These elements later joined the periodic table. -
Albert Einstein
Albert Einstein proved the existence of atoms through the mathematical use of statistics. This conformation changed the world of science immensely. -
Robert Millikan
Millikan proved the electron had a basic electric attraction using drops of oil and metal plates to see how the droplets moved around. -
Ernest Rutherford
Ernest Rutherford discovered the nucleus of an atom. -
Neils Bohr
Bohr discovered how electrons travel around the nucleus in different orbits. He created the atomic model which shows the structure of an atom. -
Henry G. J. Mosely
Mosely proved that the number of protons is unique to every element. -
Solar System Model
The Solar System Model was created by Neils Bohr and Ernest Rutherford and describes an atom as the center or "sun" which is then surrounded by "planets," which are really the moving electrons. -
Werner Heisenberg
Heisenberg contributed to the atomic theory by stating that the position of a particle cannot be known exactly. -
Erwin Shrodinger
Shrodinger found the energy levels of electrons in atoms by creating an equation to accurately calculate the information. -
Electron Cloud Model
The Electron Cloud Model is a model of an atom with a massive nucleus and an electron cloud which is meant to show how we do not know where an electron is at any given moment. -
James Chadwich
Chadwich discovered neutrons and learned that they have neither a positive nor negative charge.
