Atom Project

Heraclitus

500 BCE

Heraclitus's theory was that every thing was made of fire

Democritus

400 BCE

Democritus's model was the first conception of the idea of an atom. Democritus thought that an atom was the smallest thing there can be, he pictured it as just a circle.

Aristotle

400 BCE

Aristotle had the theory that all matter was made from four main elements Air, Water, Fire, and Earth.

Dalton

1803

Dalton defined atoms

1) All matter is composed of extremely small particles called atoms.
2) All atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties.
3) Atoms can't be subdivided, created or destroyed; atoms are indivisible.
4) Atoms of different elements combine in simple whole-number ratios to form chemical compounds.
5) In chemical reactions, atoms are combined, separated, or rearranged.

J.J. Thomson

1897

J.J. Thomson discovered the electron when he was using a Cathode Ray (A beam that carries a ray of electrons from the cathode to the anode) and magnets and saw that some particles were attracted to the positive charge. This was important because it was the first time a subatomic particle was introduced to an atom. To represent this, Thomson used the plum pudding model to demonstrate that atoms were made of electrons in a positive matter.

Rutherford

1912

In 1917 Ernest Rutherford discovered protons during an experiment where he fired positive alpha particles at gold foil with a detection ribbon circling it. He expected the particles to go through the gold foil but some deflected. Rutherford learned the particles hit very small and dense objects. He concluded that atoms have proton cores electrons surround. Dalton’s theory was wrong since protons are part of atoms, and J.J. Thomson’s plum pudding model changed to the protons and electrons apart.

Bohr

1913

Bohr discovered that atoms electrons move from different parts of the atom and produce energy when they do that.

Schrödinger

1926

In 1926 Erwin Schrödinger found that the Bohr model was was incorrect when saying that electrons move in strict orbitals. they actually move in an electron cloud.

Chadwick

1932

In 1932 James Chadwick discovered the neutron when he was finding the mass of an atom. This meant that Neutrons are added to the nucleus of the Rutherford model and atoms have more internal particles.