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340 BCE
Aristotle
Aristotle was an ancient philosopher that lived north of Greece. Aristotle did not believe in the atomic theory and he taught so otherwise. He thought that all materials on Earth were not made of atoms, but of the four elements, Earth, Fire, Water, and Air. He believed all substances were made of small amounts of these four elements of matter. This was the foundation of our knowledge about atoms today. -
309 BCE
Democritus
Democritus was an ancient philosopher that discovered that atoms were the smallest form of matter. He also theorized that they were made of what they composed which was later proven to be incorrect. Democritus believed that everything in the universe was made up of atoms, which were microscopic and indestructible. -
John Dalton
In the 1700s, Dalton lived in England. He published work about the science of color blindness and had an early scientific career. He later proposed the billiard ball model which described the basic structure of an atom. -
billiard ball model
John Dalton reinvented Democritus' idea of the atom in 1800. He believed atoms were the smallest form of matter which is a huge scientific advancement for our knowledge about them now. Dalton knew that atoms could combine and recombine with each other in whole number ratios to form compounds which led to to predict the structure of the model. -
J.J. Thompson
J.J. Thompson grew up in Manchester and was born in the late 1800s. Thompson discovered electrons and than proposed the plum pudding model later on. He also won the Adam's prize in 1884. -
plum pudding model
The Plum Pudding Model is a model of atomic structure proposed by J.J. Thomson in the late 19th century. Thomson had discovered that atoms are composite objects, made of pieces with positive and negative charge. This model was then proven incorrect by Rutherford in later years. -
Albert Einstein
Albert Einstein became famous for the theory of relativity, which laid the basis for the release of Atomic energy. He went on to become one of the most famous scientists in history. -
nuclear model
The nuclear model is a description of the structure of atoms proposed by Ernest Rutherford. The model described the atom as a tiny, dense, positively charged core called a nucleus, in which nearly all the mass is concentrated, around which the light, negative constituents, called electrons, circulate at some distance, just like the solar system. -
Ernest Rutherford
In 1911, Rutherford was the first to discover that atoms have a small charged nucleus surrounded by largely empty space, and are circled by tiny electrons, which became known as the Rutherford model of the atom. -
Neils Bohr
Neils Bohr made foundation contributions to our knowledge of atomic theory. Bohr created the bohr model which shows the atom as a small, positively charged nucleus surrounded by orbiting electrons. He also won a nobel prize in physics in 1922. -
bohr model
Niels Bohr proposed the bohr model in 1913. This is a thorough explanation about the structure of an atom. It shows hydrogen being surrounded by negative and positive ions. Successive ionization energies provide evidence for the existence of quantum shells. He came to the conclusion that electrons orbit in shells around the nucleus of an atom, the shells having discrete energy levels. -
quantum model
The quantum mechanical model is based on quantum theory, which says matter also has properties associated with waves. According to quantum theory, it’s impossible to know the exact position and momentum of an electron at the same time. This is known as the Uncertainty Principle. This was introduced by Erwin Schrödinger in 1926. -
Erwin Schrodinger
In 1926 Erwin Schrödinger, an Austrian physicist, took the Bohr atom model one step further. Schrödinger used mathematical equations to describe the likelihood of finding an electron in a certain position. This atomic model is known as the quantum mechanical model of the atom. He also proposed the wave model. -
wave model
Erwin Schrodinger introduced the idea of matter waves and demonstrated that Bohr’s orbits for the hydrogen atom were only those for which the wavelength of the electron fit exactly. -
James Chadwick
James Chadwick discovered the Neutron in atoms. Neutrons are located in the center of an atom, in the nucleus along with the protons. They have neither a positive or negative charge, but contribute the the atomic weight with the same effect as a proton. -
toroidal ring model
This model was proposed by Alfred Lauck Parson in 1915.This model explains how particles are linked together to form atoms. -
lucas model
This model was proposed by Joseph Lucas. It is a physical model that shows where electrons are located throughout the volume of the atoms. This model predicts the "magic numbers" 2, 8, 18, and 32 of electrons in the filled shells and also is able to predict why the Periodic Table of the Elements has exactly seven rows. The Lucas model also predicts the structure of the nucleus and correctly predicts hundreds of nuclide spins.
