Atomic Timeline

By: Abby Koons


Joseph Proust


He was born September 26, 1754 and died July 5, 1826. He came up with the Law of Definite Proportions. The law states "A compound is composed of exact proportions of elements by mass regardless of how the compound was created".

John Dalton


He was born September 6, 1766 and died July 27, 1844. John proposed the Atomic Theory as " All matter was composed of small indivisible particles named atoms atoms of a given element posses unique characteristics and weight, and there are three types of atoms called simple, compound, and complex".

Amedeo Avogado


He was born August 9, 1776 and died July 9, 1856. He came up with his own molecular theory. He said " Equal volumes of gases contain equal numbers molecules at the same temperature and pressure" and "gas molecules can divide during chemical reactions" .

Dimitri Mendeleev


Mendeleev was born February 8, 1834 and died February 2, 1907. At the time he knew nothing about electrons but he arranged the elements on the periodic table.

JJ Thomson


He was born on December 18, 1856 and he died August 30, 1940. He did many things in science. He proposed a model of an atom, found evidence that negatively charged particles could be taken out of an atom, and he measured the ratio of mass-to-charge for an electron.

Marie Curie


She was born November 7, 1867 and died July 4, 1934. Through her research she came up with "Radio Activity" which is the decay of Uranium and Thorium. She also discovered Polonium and Radium with help of her Husband.

Ernest Rutherford


Ernest was born on August 30, 1871 and died October 19, 1937. He conducted an experiment to learn about the atom and concluded that the grid of an atom has tiny cells and there is not a lot of positive charge. By doing this he discovered the atomic nucleus.

Niels Bohr


He was born October 7, 1885 and died November 18, 1962. He proposed a "Planetary" model of an atom. He believed that electrons are able to "jump" between energy levels or orbits.

Hans Geiger


Hans was born September 30, 1882 and died September 24, 1945. He co-invented the Geiger Counter which was a machine that counted alpha particles.

Enrico Fermi


Fermi was born on September 29, 1901 and died November 28, 1954. He conducted the first controlled chain reaction that released energy from an atom's nucleus.