Timeline Of The Evolution Of The Atomic Theory

Timeline Of The Evolution Of The Atomic Theory (B.C.E.)

Democritus and Leucippus Create First Atomic Theory (460-370 B.C.E.)

460 B.C.E. - 370 B.C.E.

The Greek philosophers, Democritus and Leucippus theorized that the world was made up of tiny particles called atoms. The word atom means indivisible in Greek.

Aristotle (384 - 332 B.C.E.)

384 B.C.E. - 332 B.C.E.

Aristotle thought differently than Democritus; he thought that the world was made up of air, water, fire, and earth, instead of tiny particles. Aristotle's ideas were used by the Catholic church in the middle ages, and the people who followed Democritus, were shunned or killed.

Timeline Of The Evolution Of The Atomic Theory (1 To 2000 C.E.)

Sir Isaac Newton (1643 - 1727 C.E.)

1643 C.E. - 1727 C.E.

Newton formed a theory of light, that light was made up of particles. He also formed the three laws of motion.

1)If an object is moving at a constant speed, it won't move unless you force it to speed up or slow down.

2)The acceleration of an object depends on the strength of the overall force applied to it as well as on the mass of the object.

3)With every action, there is a reaction.

John Dalton (1766 - 1844 C.E.)

1803 C.E. - 1884 C.E.

John Dalton believed in Democritus' work. His theory consisted of four basic ideas:
1) All matter is composed of atoms that are indivisible.
2) All atoms are identical in properties, such as size and mass.

3) Atoms are rearranged as a chemical reaction occurs.
4) Compounds are formed by combination of multiple atoms.
5) They cannot be created or destroyed.



Eugen Goldstein (1850 - 1930 C.E.)

1850 C.E. - 1930 C.E.

In 1886, Goldstein helped contribute to the events that lead to the discovery of the proton. He observed the changes in a cathode ray tube, and discovered the anode rays, positively-charged particles that moved in the opposite direction, from the anode to the cathode. His work helped Rutherford.

J.J. Thomson (1856 – 1940 C.E.)

1856 C.E. - 1940 C.E.

In 1897, J.J. Thomson discovered the electron. His work proved one of Dalton's ideas wrong, the atom was not indivisible, but in fact made up of multiple components. The discovery was made when he conducted an experiment with a cathode ray tube, when an electrical current was passed through, glowing material could be seen. When he put two electrically charged plated on opposite ends of the tube, the light was bent on the positive plate. Thomson thought that the atom looked like raisin pudding, a ball with negative electrons clumped on it.

Max Planck (1858 - 1947 C.E.)

1858 C.E. - 1947 C.E.

Called the father of quantum physics, invented the quantum theory. Quantum physics is mathematical interaction between particles in matter. Einstein used the quantum theory.

Hantaro Nagaoka (1865 - 1950 C.E.)

1865 C.E. - 1950 C.E.

He disliked Thomsons model of the atom, and created his own. A model that resembled Saturn with its rings; the rings were the electrons and the sphere was the positive center. Hantaro's model was not accurate, and it was left to Bohr and Rutherford to fix that.

Robert Andrews Millikan (1868 - 1953 C.E.)

1868 C.E. - 1953 C.E.

Millikan is credited for finding the charge and mass of an electron. He did so by conducting the oil drop experiment in 1909. he put a charge on a tiny drop of oil, and measured how strong an electric field had to be, to stop the oil drop from falling. The mass was 9.10938291 × 10 -28 grams, and the charge was -1.

Ernest Rutherford (1871 – 1937 C.E.)

1871 C.E. - 1937 C.E.

In 1908, Ernest Rutherford proved Thomson's atomic model to be incorrect. He is famous for his gold foil experiment which stated the existence of protons. He shot alpha particles at the gold foil, and observed where they hit. Most were undeflected, while the rest bounced off in different directions.

Albert Einstein (1879 - 1955 C.E.)

1879 C.E. - 1955 C.E.

Einstein is famous for his theory of relativity, and his equation on mass–energy equivalence. E = mc² states that mass and energy is the same thing. The theory of relativity is split into two theories: special relativity, and general relativity.

Relative means in relation with something else, so the special relativity theory states that the speed of light is always constant, no matter from what perspective it is viewed in.

The general theory states that space and time works together. Empty space-time without gravity is flat, however space with matter is curved by gravity. These curves cause time to run slowly. Gravity also bends light by bending the median it travels in: space.

Neils Bohr (1885 - 1962 C.E.)

1885 C.E. - 1962 C.E.

In 1913, Neils Bohr created a new model of the atom. It consisted of electrons that orbited in "shells" or layers around the nucleus. As the energy level changed, so did the location of the electron. Neils Bohr was also the first to introduce the idea of the quantum mechanical model, where a cloud of electrons surrounds the nucleus.

Erwin Schrödinger (1887 - 1961 C.E.)

1887 C.E. - 1961 C.E.

Erwin Schrödinger built upon the quantum mechanical model. He used a mathematical equation to describe the odds of finding the location of an electron, he called the layers, orbitals. These orbitals could be described as "electron density clouds".

James Chadwick (1891 - 1974 C.E.)

1891 C.E. - 1974 C.E.

In 1932, James Chadwick proved the existence of neutrons. He shot alpha particles (two protons and two neutrons bound) at a sheet of beryllium, that filtered out the electrons. The neutrons hit a sheet of paraffin wax. The ones that filtered through the paraffin wax were the protons.

Chadwick discovered that neutrons help reduce the repulsion between protons to stabilize the atom's nucleus. Neutrons always reside in the nucleus of atoms, and they are about the same size as protons. However, neutrons have no charge (a charge of 0).

Satyendra Nath Bose (1894 - 1974 C.E.)

1894 C.E. - 1974 C.E.

He discovered the boson, a subatomic particle. Bose worked with Einstein. They both found the Bose–Einstein condensate, a state of matter where a drop in temperature occurs to bosons.

Enrico Fermi (1901 - 1954 C.E.)

1901 C.E. - 1954 C.E.

Developed the nuclear reactor, and also contributed to the quantum theory. Worked on the Manhattan Project, the secret project to develop the first atomic bomb.

Timeline Of The Evolution Of The Atomic Theory (21st Century)

Discovery Of Photonic Molecule (2012 C.E.)


MIT discovered photon particles that can bind to form molecules. Researchers thought that it could be similar to the sci-fi "lightsaber" from the Star Wars series. This discovery may help create better quantum computers.

Peter Higgs (1929 C.E. - Present)

2012 C.E.

The Higgs Boson particle (or god particle) was speculated by Peter Higgs in 1964. Thought, recently, the particle has been discovered by CERN in 2012. It proved the existence of the Higgs field, and stated that the god particle gave the other particles mass.

The Higgs field occupies everything in the universe. It is visualized as molasses that drags particles that move through it. Particles that interact with the Higgs, receive mass. So electrons that hardly interact with the field have very little mass, and protons and neutrons that interact with it regularly have more mass.

The god particle's existence was proved in the Large Hadron Collider at CERN. There are protons that are smashed together to relesase energy; since Einstein's theory of relativity states that mass is energy and energy cannot be destroyed, new particles are created from the release of energy. The Higgs is unstable, therefore it splits into more particles. The sensors in the collider detected this rare occurrence. It is rare because there are trillions of collisions occurring.

Alan Guth (1947 C.E. - Present)


Alan Guth had a theory in the 1970s, called inflation. Inflation builds upon the Big Bang theory; the big bang theory states that the universe is constantly expanding, the inflation theory states that the universe expands at different speeds at different times. The inflation period is less than a second where the universe almost doubles in size. There is evidence in 2014, that inflation exists. The cause of it is gravitational waves.