Timeline of Atomic Theory

Alchemists

700 BCE

400-1400 BCE. Their main goal over the years was to turn lead and some other metals into gold. This started the conversation of how all different materials are somewhat connected to each other, sparking the creating of the periodic table many years into the future.

Ancient Greeks

500 BCE

(Democritus) 460-500 BCE
He founder of the atomic theory, who theorized that everything is made of tiny particles called atoms. The atoms have empty space between them, Atoms are indestructible and that their are infinite number of atoms. (Empedocles) 494-530 BCE
He theorized that everything is made of different combinations of Air, Earth, Water and Fire.

Asharya Kanada

200 BCE

Estimated to live sometime fro 600-200 BCE
Kanada was very ahead of his time. At this time the Greek's and Alchemist had the atom all wrong but Kanada was very close. He theorized that everything is made up of this tiny thing called a atom, and how it is indivisible and cannot be destroyed.

Dalton

1810

1776-1844
Although the atomic theory was later proved correct by Einstein, the original founder of the theory was Dalton. He created and published the still relevant rules of a atom.

1. Matter is made up of atoms that are indivisible and indestructible.
2. All atoms of an element are identical.
3. Atoms of different elements have different weights and different chemical properties.
4. Atoms of different elements combine in simple whole numbers.
5. Atoms cannot be created or destroyed.

Satyendra Nath Bose

1895

1894-1974
Satyendra Nath Bose's greatest achievement was discovering the theory that was adopted by Einstein, called the Bose-Einstein condensate. Commonly refereed as a Bose it is when a gas is cooled down which makes the particle act as a wave, and eventually the more it cools down the waves get bigger and eventually turn into a super wave. This increased are understanding of how waves and particles act.

J.J Thomson

1897

1856-1940
J.J Thomson while working with cathode rays(Negatively charged) and positive charged neon particles that the previous atomic model was wrong. He proved the existence of electrons. He theorized that electrons were floating around the atom and the atom was a big clump of positively charged proton. Creating the plum pudding model.

Marie Sklodowska Curie

1898

1867 –1934
Marie Curie discovered many things from radium to polonium and the creation of X-rays. But her main discovery that led to all of the others was radioactivity. Radioactivity is when a unstable nucleus decays that provides energy and heat. This is used to make pretty much all of the technology that uses waves from the electromagnetic scale, because this energy increase with decay causes the waves. This is how she discovered x Rays

Max Plank

1900

1858-1947
Planks discovered that energy of the light is directly proportional to the frequency. How this relates the the atomic model is that energy transferred from different shells of the atom created a frequency, which with his theory made energy. Creating Plank's Quantum theory of radiation. This information explaining the electromagnetic spectrum as we know it and how the atom explains the phenomenon of gamma rays to visible rays to radio waves.

Hantaro Nagaoka

1904

1865 – 1950
Hantaro Nagaoka questioned the planetary model of the atom, with his own studies and test he determined that the atoms rings were similar to Saturn rings. How instead of one electron, that their was a number of electron orbiting each rings of the atom

Albert Einstein

1905

1901(Got his Degree)-1955(Death) He proved the existence of atoms by using something called "Brownian Motion" It showed that when tracking particles, their movement is completely random. Which shows that that everything is built up from individual things called atoms. He also proved with the theory of relativity that mass and energy can easily be changed proving the power and destruction of the atom.

Ernest Rutherford

1911

1871-1937
Rutherford while testing what would happen if you shot alpha particles at gold foil, found that instead of all of the rays going through at around 90 degrees. That some particles were bouncing at very different/random angles, which he later found out was the nucleus. With this evidence he concluded that atoms have a positively charged nucleus, most of it was space and electrons at the outer part of the atom.

Niels Bohr

1913

1885-1962
Niels Bohr greatest discovery was the editing and finalizing the Rutherford model. He theorized that electrons orbit the nucleus in multiple orbit shells, thus creating the new Bohr-Rutherford Diagram and leading to the discovery of how energy levels can be quanta sized with each orbit shell.

Louis de Broglie

1924

1892-1987
Broglie created the idea that electrons, can also be described as wavelengths. Vise versa that light can be shown as wavelength or particle. Thus leading to his final conclusion that nature of electrons and suggested that all matter have wave properties.

Wolfgang Pauli

1925

1900-1958
He made the discovery that no two electrons can have the same quantum numbers meaning that no two electrons are the same in each atom. This principle is what sparked the creation of quantum numbers, with the knowledge that no two electrons are identical

Werner Heisenberg

1925

1901-1976
Heisenberg proved with the knowledge that everything can be represented with either a particle or a wavelenght. That we can never know the exact position and the momentum of a object can not be known at the same time. And because wavelengths and particles have different location and momentum graphs that cannot be combined, shows that you cannot know both at the same time. Creating the uncertainty principle.

Erwin Schrödinger

1926

1887-1961
Schrödinger took the Bohr-Rutherford diagram one step further by theorizing that it is nearly impossible to guess where the exact position of the atom was, so he created what known to this day as the quantum mechanical model of the atom. Instead of showing energy rings, he showed dense clouds around the atom showing where the highest probability of the electron was, the denser the area of the cloud the higher probability of it being their.

James Chadwick

1932

1891-1974
James Chadwick discovered Neutrons in atoms.
He did this with the experiment that beryllium and alpha particles with a radioactive produced neutral radiation. He measured the mass found that it was close to protons. This with the knowledge that this particle, added the the removed protons of the experiment added together to get a similar mass of the substance, cemented his theory that neutrons with protons made the nucleus.

Irène Joliot-Curie

1933

1897 – 17 March 1956
Irène Joliot-Curie built on what her mother (Marie Curie) discovered on radioactivity. She discovered that radioactive elements can also be made from stable normal elements. She discovered when mixing radioactive elements with aluminum, the aluminum turned radioactive

Lise Meitner

1938

1878 –1968
Lise Meitner was one of the main scientist that discover what nuclear fission is and what can it do, which is make bombs. Nuclear fission is when a neutron or another tiny particle gets launched into a target big nucleus to split and create a large amount of energy that get sent out.

Ronald J. Gillespie

1977

1924-Present
Ronald J. Gillespie's main achievement in atomic theory is his idea and studies of VESPR models. What this means is that electron pairs repels bonded electrons. This is what creates the famous V shape in Water(H20)

Richard F. W.

1991

1931 – 2012
Richard discovered that electron density is a key factor of a atoms behavior. This idea at first was widely looked down upon at first, but now the theory is the mostly accepted by scientists.

Robert J. LeRoy

1995

1943 – 2018
Robert J. LeRoy is known for his discoveries and studies of forces, more specifically inter and intra molecular forces and how they are drawn out. His biggest discovery was the LeRoy Radius(the internuclear distance between two atoms)