Atomic Model Timeline

The Alchemist

1720 BCE

Alchemy helped put the Atomic Theory in place by making the Periodic Table of Elements. The periodic table came from breaking down the chemical composition of Fire, Earth, Wind, and Water.

Aristotle

450 BCE

Aristotle composed a theory based on the fact that he though everything was composed of 4 elements. At this time Aristotle and Democritus were two popular philosophers but Aristotle was more popular. This made his theory more popular. Aristotle's theory was actually wrong and Democritus' was right which pushed back advances in the atom for a bit.

Democritus

400 BCE

Democritus discovered the atom. He discovered that everything was made of these tiny things called atoms and that between every atom there is space. He also discovered that atoms are always in motion and that they are indestructible.

Plato

427

Plato's discovery, known as the 4 element theory, or the Platonic theory, helped to shape the atomic theory by setting a base of how atoms break down.

Robert Boyle

1661

Robert Boyle got rid of the idea that there are 4 elements and discovered substances that can be broken into more than one substance called an element. An element is simply a substance made from only one atom which helps science.

Lavoisier

1778

He did experiments with oxygen and found that it is an element. He also made the 1st table of elements that people today would agree with.

John Dalton

1803

Dalton came up with the atomic theory saying that all matter is made up of atoms. He also discovered that although in an element all the atoms are identical, there can be different size and mass of different elements.

Dmitri Mendeleev

1869

He invented the periodic table of elements.

JJ Thompson

1897

Thompson came up with the idea that al atoms have very small negatively charged subatomic particles/electrons. He was also the creator of the Plum Pudding model.

The Curies

1898

Curie researched radioactivity. She contributed to the study of radium and radiation by discovering 2 new elements: radium and polonium.

Albert Einstein

1905

While trying to make an energy efficient fridge, Einstein discovered that energy and mass can be interchanged, allowing him to understand nuclear power and atomic weapons in a much needed time (WWII). He came up the equation E=mc2.

Robert Milikan

1910

While trying to measure the charge of an electron by doing the oil drop experiment, Milikan suceeded and found the exact magnitude of the electron's charge.

Ernest Rutherford

1911

Ernest Rutherford studied radiation and discovered that there are 2 different types of radiation, alpha and beta. He found that helium gas could be formed from radioactive substances.

Neils Bohr

1913

Bohr composed a theory based on quantum theory. He discovered that energy is transferred only in certain well defined quantities. He found that the reason atoms created light in fixed wavelengths is because electrons should move around the nucleus but only in certain orbits. When going from one orbit to a different orbit that has a lower energy when lighting, quantum is released.

Henry G. J. Mosely

1913

Mosely was able to prove that the major properties of an element are not determined by atomic weight, but rather the atomic number. He was able to understand how atomic number and the charge of the atomic nucleus work together.

Werner Heinsenberg

1925

Heinsenberg came up with the theory of quantum mechanics. Quantum mechanics is "science dealing with the behavior of matter on the atomic and subatomic scale." He also helped make the first west German nuclear reactor.