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415 BCE
Democritus Theorizes the First Atomic Theory
Greek philosopher Democritus first theorized that our universe was made up of tiny particles of matter, binding everything together. -
Dalton’s Atomic Theory
John Dalton was the first scientist to state the atomic theory, that the whole universe was made up of tiny indestructible particles called atoms. He also first published a table of atomic weights for six different elements hydrogen, oxygen, nitrogen, carbon, sulfur and phosphorus). -
Becquerel Discovers Radioactivity
From the intensive research he conducted, along with the Curies, he was able to prove radioactivity existed within atoms, forcing other scientists to change their theoretical model of the atom, proving that atoms were indestructible. -
Thomson Discovers the Electron
J.J. Thomson first proposed his theory that cathode rays were composed of certain unknown particles, deemed smaller than atoms, or subatomic. These were negatively charged, and are now called electrons. -
The Curies Develop Atomic Physics
Through radioactivity, Marie and Pierre Curie were able to discover two new elements, radium and polonium. Their developments of radioactivity led to the field of atomic physics, and are directly responsible to the development of the atomic bomb. -
Planck’s Theory of Quantum Energy
Max Planck first developed the quantum theory of energy through his work in thermodynamics, which significantly contributed to the understanding of the atomic and subatomic processes. -
Einstein Mathematically Proves Atoms Exist
Albert Einstein proved that atoms exist, most prominently through the idea of liquid being made up of atoms, meaning that no matter what, they are in constant motion. This motion accelerates or slows down depending on the heat and light around them. -
Rutherford Discovers the Nucleus
Ernest Rutherford discovered through examination with a gold sheet, that the majority of atomic matter was made up of a nucleus, sitting at the centre of an atom, harvesting electrons. -
Bohr Makes First Theoretical Representation of the Atom
Bohr first sketches the atom, stating that electrons were harvested in a fixed position around the nucleus, orbiting in an equal distance away from it. -
Schrödinger Proves There isn’t a Definite Position for an Atom
Schrödinger further developed the theory of electrons being present and being random in an atom, creating equations to determine the probability of an electron’s position. -
Broglie States That All Matter Has Wave Properties
Louis de Broglie first calculated the wave nature of electrons, and further stated that all matter had some sort of wave property. This was a groundbreaking contribution to the quantum theory, and the movement of electrons. -
Chadwick Discovers the Neutron
James Chadwick discovered the neutron, a particle sitting at the core of the nucleus and being distinct from the proton. This discovery also eventually led to the development of nuclear power and the atomic bomb.
