History of the Atomic Model

History of the Atomic Model

Rutherford (1911)

J.J Thompson (1897)

Michael Faraday (1830)

Joseph Proust (1794)

Democritus (400 B.C.)

Chadwick (1932)

Thomson's Plum Pudding Model

Chadwick discovered the third sub-atomic partical, He named it the ‘neutron’.

He first published his Law of Definite Proportions in 1794. This law states that a compound is composed of exact proportions of elements by mass regardless of how the compound was created.

He is the first scientist to create a model of atom. He discovered that all matter is made up of invisible particles called atoms. He also discovered that the atoms are solid, indestructible and unique. His model was just a round solid ball. He didn't knew about electrons or nucleus.

He found that atoms have nucleus by using his gold foil experiment. By using a radioactive source, he sends alpha rays to a gold foil. Most of the aplha particles travel trough the gold foil but some of them get deflected. So Rutherford understoods that atom is mostly empty and has a nucleus inside it.

He made one of the most significant discoveries that led to the idea that atoms had an electrical component. Faraday placed two opposite electrodes in a solution of water containing a dissolved compound. He observed that one of the elements of the dissolved compound accumulated on one electrode, and the other element was deposited on the opposite electrode. It was clear to Faraday that electrical forces were responsible for the joining of atoms in compounds.

In the plum pudding model, electrons were

represented by plums and the atom was represented by the pudding. By this model, Thomson wanted to show that electrons are randomly traveling inside the atom, just like some plum particles in a pudding

Bohr (1922)

George Johnstone Stoney (1891)

John Dalton (1803)

Lavoisier 1780

Robert Millikan (1909)

He was first to discover that electrons travelled in different orbits. He said that number of electrons in the outer orbit determines the properties of an element.

Stoney suggested that a subatomic particle existed, which was a particle of electricity held within the atom, named the electron, which was made up of separate negative particales. This helped us understand that within the atom, there are other particles and that atoms have a charge.

He suggested that compounds formed by two or more dissimilar kinds of atoms. He also believed atoms are like billiard ball. Also he believed that atoms of a given element are identical in size, mass, and chemical properties.

He is a french nobleman that founded several elements and put the first table of elements together. He found the Law of Conservation of Mass. The law states that matter cannot be made or destroyed.

Millikan measured the charge on an electron with his oil-drop apparatus. With his oil-drop experiment, he successfully measured the charge and mass of an electron.

The Quantum Atomic Model

Chemical Reaction = Rearrangement

Law of Conservation

of Mass

According to quantum theory, we cannot find the exact place of the electrons and their orbits. Heisenberg, De Broglie and Schrödinger said that electrons only exist in certain energy levels which are described by quantum numbers.

Kaan Kanatli