-
500 BCE
The Alchemists
Created equipment and a scientific process that would allow for the discovery of the atom. Were the first people do use the term "element" when referring to a chemical. -
440 BCE
Plato
Theorized that solid forms of matter were composed of invisible elements shaped like triangles. He proposed that the elements were "all around us." -
400 BCE
Democritus
Suggested that all matter was made of tiny discreet particles and that the properties of the particles determined the properties of the matter. -
Robert Boyle
Theorized that all matter was composed of tiny particles which he named "corpuscles." -
Antoine Lavoisier
Established the law of conservation of mass and studied reactions of elements to oxygen. -
John Dalton
Proposed an atomic theory regarding spherical atoms with measurable properties of mass. -
Billiard Ball Model
John Dalton -
Amedeo Avogadro
Proposed the equal volumes of gases of the same temperature and pressure contain the same number of molecules regardless of physical and chemical nature and properties. -
Dmitri Mendeleev
Organized seven groups of elements with similar properties and came up with the Periodic Law. -
JJ Thompson
Used a CRT to uncover the charge to mass ratio of an electron. Proposed the Plum Pudding Model. -
The Curies
Proposed that radioactivity doesn't depend on how the atoms are arranged into molecules, rather, it depends on the origins of the atoms themselves. -
Plum Pudding Model
J.J. Thompson -
Albert Einstein
Mathematically proved the existence of atoms. -
Robert Millikan
Conducted the oil-drop experiment which uncovered the charge and mass of an electron. -
Ernest Rutherford
Performed the gold foil experiment establishing the structure of an atom visually. Disproved the Plum Pudding Model and created the Planetary Model. -
Planetary Model
Ernest Rutherford and Niels Bohr -
Henry G. J. Mosely
Determined the charges of most atoms using x-ray tubes. Responsible for the Periodic Table arrangement based on atomic number. -
Neils Bohr
Came up with an explanation of atomic structure that explained the regularities of the Periodic Table. -
Erwin Schrodinger
Produced papers that gave the foundations of quantum wave mechanics. -
Electron Cloud Model
Erwin Schrödinger and Werner Heisenberg -
Werner Heisenberg
Formulated a type of quantum mechanics based on matrices and proposed the “uncertainty relation”, setting limits for how the position and velocity of a particle can be determined. -
James Chadwick
Used alpha particles to discover the existence of neutrons.