Atomic Discoveries

Events

The Discovery of Atoms

400 BC

Democritus concluded that all matter is made up of tiny discrete particles called atoms

John Dalton's Atomic Theory

1803

John Dalton concluded that matter is composed of indivisible buliding blocks. Additionally, he stated that all atoms of a given element are made up of the same mass and properties.

J.J. Thomson's Atomic Theory

1897

J.J. Thomson discovered that the atom consists of particles called electrons that are surrounded by a positive charge to neutralize their negative charge.

Ernest Rutherford's Atomic Theory

1911

Rutherford discovered that the atom consists of a densely hard center called a nucleus that is heavy. He concluded that an atom primarily consists of empty space.

The First Atomic Model

1913

The first ever atomic model was created by Neil Bohr. In this model, it is revealed that the atom is a small nucleus that is positively charged and surrounded by electrons in orbit.

The Wave Mechanical Model (Modern Day Atomic Model)

1926

Austrian physicist Erwin Schrodinger made the wave mechanical model as he combined the equation of the behavior of waves with the de Broglie equation to create a mathematical model of the distribution of electrons in an atom. He concluded that the atom primarily consists of space and has a dense nucleus

The Discovery of the Neutron

1932

The neutron was discovered by James Chadwick when he bombarded atoms of beryllium atoms with alpha particles and discovered an unknown radiation. He learned that the neutron is located within the nucleus, has a neutral charge, and has the same atomic weight as a proton.