Chem Atomic Theory

Democritus - 370 B.C.

400 BCE

Democritus said that an atom is the smallest piece of matter but never figured out how to measure them. He also concluded that everything is made up of atoms and that they are always moving. He said that an atom is the smallest piece of matter but never figured out how to measure them. He also concluded that everything is made up of atoms and that they are always moving.

Antoine Lavoisier - 1743

1789

Lavoisier found that matter was made of atoms that weren’t created nor destroyed during chemical reactions. He found this out by constructing a model to display a chemical change while demonstrating that the mercury oxide didn’t lose mass when it reacted.

John Dalton - 1766

1804

Dalton created his own Atomic Theory. There were five statements that he found: Atoms cannot be subdivided, created or destroyed, atoms of different elements can combine to create compounds in whole number ratios, in chemical reactions atoms are combined, separated, or rearranged, and that all matter is composed of atoms.

Dmitri Mendeleev - 1834

1869

Mendeleev used the properties and similarities of different elements to create a table to organize them. In doing so, he created a base model for the present-day periodic table, and predicted some elements and their properties.

Eugene Goldstein - 1850

1886

Goldstein found and proved the existence of a positively charged particle known as the proton. He achieved this by using a cathode ray tube with holes in it.

JJ Thomson - 1856

1904

JJ Thomson contributed a lot in the field of Atomic theory in two main discoveries. These two discoveries were finding the mass-to-charge ratio of electrons and proposing the plum pudding model to represent the configuration of atoms.

Earnest Rutherford - 1871

1911

Rutherford discovered that there was a small, central nucleus in an atom that contained most of the mass of the atom.

Niehls Bohr - 1885

1913

Bohr created a model to depict the configuration of the electrons in an atom. This model shows the rings and energy levels of the electrons by their mean distance from the nucleus.

Erwin Schrödinger - 1887

1926

Schrödinger created the quantum mechanical model; this is a model stating how electrons are simultaneously in all of the possible places it could be while orbiting around the nucleus, using 4 different quantum numbers to define each electron. He also discovered that electrons could exhibit properties of both particles and waves.

James Chadwick - 1891

1935

James Chadwick discovered the neutron. He achieved this by bombarding beryllium with particles to split the nucleus and found the emission of proton-like particles.