The Timeline of the Atom

Plato 400 b.c

• Plato thought that a Fith atomic type must exist, which was later called ether that was made up of the objects in the heavens.

Democritus 430 b.c

• Democritus believed that everything in the universe was made up of atoms, which were microscopic and indestructible.

Alchemists 700-1500 b.c

• Alchemists believed they could make different metals out of gold.

solar system

Robert Boyle 1670

• Robert thinks that gas or oxygen is made out of atoms.

Robert Boyle

Antoine Lavoisier 1789

• Antoine experimented with burning and named oxygen.

Dmitri Mendeleev1789

• Dmitri published a periodic table and also arranged the elements known at the time in order of relative atomic mass.

John Dalton 1803

• John's theory was all matter is made of atoms. All atoms of a given elements are identical in mass and properties. Compounds are formed by a combination of two or more different kinds of atoms. A chemical reaction is a rearrangement of atoms

solid sphere

Amadeo Avogadro 1810

• Amedeo is best known for his hypothesis is that equal volumes of different gases contain an equal number of molecules, provided they are at the same temperature and pressure.

J.J Thomson 1897

• J.J discovered the electron by or experimenting with a Crookes,or cathode ray,tube. He demonstrated that cathode rays were negatively charged, in addition,he also studied positively charged particles in neon gas.

J.J Thomson

plum pudding

Albert Einstein 1905

• Albert treated matter and energy as exchangeable. Albert became famous for the theory of relativity,which laid the basis for the release of atomic energy.

Albert Einstein

The Curies 1890-1910

• In 1898 the curies announced the discovery of two new elements radium and polonium.

Ernest Rutherford 1911

• Ernest famed the gold foil experiment of 1909 demonstrated that atoms were made up of a charged nucleus orbited by electrons.

Henry Mosely 1913

• Henry developed the application of x-ray spectra to study atomic structure.

Henry Mosley

Niels Bohr 1913

• Bohr was the first to discover that electrons travel in separate orbits around the nucleus and that the number of electrons in the outer orbit determines the properties of an element.

Niels Bohr

Robert Millikan 1923

• Robert was credited with the discovering of the value for electron charge,through the famous oil drop experement.

electron cloud