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The Alchemists discovered the 4 basic elements which became the basis for the periodic table of elements. The elements were water, fire, wind, and earth. -
Democritus created the term and introduced the idea of an atom. He theorized that all material bodies are made up of invisible, small atoms. -
Plato found that there are 5 solid shapes whose sides are made from regular polygons. He was convinced that atoms of matter must derive from the 4 fundamental solids. -
Robert Boyle, known for his famous Boyle's law, proposed that all substances are made up of corpuscles or atoms of various types and sizes. He proposed and published this in the same year. -
Antoine Lavoisier found that the total mass of products and reactants in a chemical reaction is always the same. It took him from 1772-1794 to propose and publish it. -
The Billiard Ball Model was created by John Dalton and was published in 1803. -
John Dalton discovered the atomic theory. He proposed the theory in 1803 but published it in 1808. His theory states that all matter is made of atoms, which are indivisible. -
Amedeo Avogadro concluded that elementary gases such as hydrogen, nitrogen, and oxygen were composed of two atoms. He also proposed that equal volumes of gas contain equal numbers of molecules. -
Dmitri Mendeleev developed the periodic table of elements in which the the elements were arranged in order of matching atomic weight. -
Robert Millikan discovered that there is a fundamental electric charge in an atom which was the charge of the electron. He founded the electron in the 1890s. -
JJ Thomson's experiments with cathode ray tubes showed that all atoms contain tiny negatively charged subatomic particles or electrons. -
Pierre and Marie Currie conducted an experiment on uranium rays and discovered that they remain constant and they claimed the rays came from the element's atomic structure. This theory created the field of atomic physics. -
The Plum Pudding Model was created by JJ Thompson and was published in 1997 -
Albert Einstein created an atomic theory that mathematically proved the existence of the atom. He proposed and published his theory in the same year. -
Ernest Rutherford founded that the atom consists of mostly empty space with its mass concentrated in a central positively charged nucleus. He basically founded the nucleus of an atom. -
Neils Bohr proposed a theory for the hydrogen atom stating based on quantum theory that some physical quantities only take discrete values. He proposed the theory and published it in the same year. -
Henry Mosley concluded that the atomic number in an atom is the number of positive charges in an atomic nucleus. He also stated that there were three unknown elements, with atomic numbers 43, 61, and 75, between aluminum and gold. -
The Solar System Model was created by Ernest Rutherford and Niels Bohr and published in 1897. -
Werner Heisenberg contributed to atomic theory through formulating quantum mechanics in terms of matrices and discovering the uncertainty principal which states that the particles position and momentum cannot both be known exactly. -
The Electron Cloud Model was created by Erwin Schrodinger and was published in 1926. -
James Chadwick discovered that atoms consisted not only of protons and electrons but also neutrons. He also found neutrons occupy the nucleus of the atom.