The discovery of the Atom ( Estefanía Lasso and María Alejandra Anaya)

Democritus

400 BCE

Democritus's idea was that matter consists of invisible particles called atoms and a void (empty space).He was the first person to use the term atom that means indivisible).

John Dalton

1800

He was the first to adapt Democritus’ theory into the first modern atomic model.

William Crookes

1861

Crookes' is responsible for reconstructing the Cathode Ray, discovered the element thallium and show there is a negative charge in atoms.He discovered the thallium in 1861

J.J Thomson

1890

J.J Thomson is credited for discovering the electron. He used his research on cathode ray tube technology in this discovery. Using what he had discovered, Thomson predicted what an atom should look like.

Niels Bohr

1910

Niels Bohr agreed with the planetary model of the atom, but also knew that it had a few flaws. Using his knowledge of energy and
quantum physics he was able to perfect Rutherford’s model. He was able to answer why the electrons did not collapse into the nucleus.

Robert Millikan

1910

Robert Millikan was a physicist who discovered the elementary charge of an electron using the oil-drop experiment. He also proved that this quantity was a constant for all electrons.

Ernest Rutherford

1911

Rutherford's gold foil experiment showed that the atom is mostly empty space with a tiny, dense, positively-charged nucleus. Based on these results, Rutherford proposed the nuclear model of the atom.

Henry Gwyn Jeffreys Moseley

1914

Henry Moseley discovered the atomic number of each element using x-rays, which led to more accurate organization of the periodic table.

Erwin Schrödinger

1920

Erwin Schrödinger was a revolutionary physicist who used Heisenberg’s uncertainty principle to come up with the atomic model that we still use today.

James Chadwick

1932

Chadwick made a fundamental discovery in the domain of nuclear science: he proved the existence of neutrons – elementary particles devoid of any electrical charge.