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500 BCE
The Alchemists
The Alchemists proposed that all metals were formed of sulfur and mercury in different proportions. This ended up being false, but this was important because it started a conversation about what makes up matter. -
440 BCE
Plato
Plato said that all matter is a copy of an "ideal form" that is unchanging. He also said that matter could be divided into smaller and smaller units infinitely. -
400 BCE
Democritus
Democritus formed a hypothesis about the universe, he posed that everything was made up of atoms. -
Robert Boyle
Robert Boyle demonstrated that matter is made up if smaller particles. These particles are now known as atoms. -
Antone Lavoisier
Antone Lavoisier discovered oxygen and named it. He also studied how it behaves and combusts. -
John Dalton
John Dalton discovered that each element had its own unique kind of atom. -
Billiard Ball Model
The Billiard Ball Model was the first atomic model created by John Dalton. It shows how atoms join together to form molecules. -
Amadeo Avogadro
Amadeo Avogadro posed that equal volumes of gasses will contain the same number of molecules. -
Dmitri Mendeleev
Dmitri Mendeleev created the first version of the periodic table of elements. -
JJ Thompson
JJ Thompson discovered the electron, which was the first subatomic particle to be found. -
Pierre and Marie Curie
Pierre and Marie Curie confirmed that some elements were radioactive. And discovered multiple new elements. -
Plum Pudding Model
The Plum Pudding Model was created by JJ Thompson, it showed the "pudding" as the positive charged atom, and the "plums" in the pudding as the negative charged electrons. -
Albert Einstein
Albert Einstein Mathematically proved the existence of atoms. -
Robert Millikan
Robert Millikan discovered electrons. And measured the charge of an electron. -
Solar System Model
The Solar System Model was created by Ernest Rutherford and it shows the nucleus int the center (like the sun) surrounded by electrons (like planets orbiting the sun). -
Henry G.J. Mosely
Henry G.J. Mosely justified the concept of the atomic mass of elements. -
Neils Bohr
Neils Bohr made an atomic model where the electrons surround the nucleus. -
Ernest Rutherford
Ernest Rutherford discovered the proton and developed an atomic numbering system. He also discovered radioactive half-life which is a way to figure out how old rocks and minerals are. -
Electron Cloud Model
The Electron Cloud Model shows a nucleus in the middle and a cloud of energy (electrons) surrounding it. -
James Chadwick
James Chadwick was the first person to discover the neutron. -
Erwin Schrodinger
Erwin Schrodinger advanced the field of quantum mechanics and wave theory (how subatomic particles function).