-
340 BCE
Aristotle
(Although his theory didn’t start circulating until the 17th century) Aristotle’s theory contradicted Democritus’ theory completely. He believed that an object did not have separate parts (aka atoms), that they were just one. He also believed that everything that existed was a combination of earth, fire, water, and air. -
1 BCE
Democritus
Fifth century B.C. 1, Everything is composed of “atoms”, which are physically, but not geometrically, indivisible, between atoms, there lies empty space, atoms are indestructible, atoms have always been, and always will be, in motion, there are an infinite number of atoms, and kinds of atoms, which differ in shape, and size. -
Antoine Lavoisier
The first breakthrough in the study of chemical reactions, he found that mass is conserved in a chemical reaction. He created the numbers for the elements. -
Joseph Louis Proust
Law Of Definite Proportions: a compound is composed of exact proportions of elements by mass, regardless of how the compound was created. Compounds always combine in constant proportions. -
John Dalton - The Elemental Model and The Billiard Ball Model
All matter is made of atoms. Atoms are indivisible and indestructible. All atoms in an element are the same size, shape, and volume. Compounds are formed by the combination of two or more different kinds of atoms. A chemical reaction is the rearrangement of atoms. Elemental Model- John Dalton proposed that all matter is composed of very small things which he called atoms. Billiard Ball Model - Around the 1800’s, Dalton thought atoms were the smallest particles, he imaged them as spheres. -
JJ Thomson - The Plum Pudding Model
Discovered the electron when experimenting. He demonstrated that cathode rays were negative. He also studied positively charged particles in neon gas. Plum Pudding Model - 1897, The Plum Pudding Model is a model of atomic structure made of pieces with positive and negative charge, and that the negatively charged electrons within the atom were very small compared to the entire atom. -
Marie Curie
Her and her husband discovered two new elements: radium and polonium. The study of radium later contributed to the atomic bomb and x-rays. -
Max Planck
The German physicist proposed his idea of the quantum theory in which describes the unusual behavior in photons, protons, and other small particles. He received a Nobel Prize in 1918. -
Albert Einstein
1905 Albert Einstein showed his theory of relativity, which explains the gravitation of planets and how it’s affected by mass and energy. -
Ernest Rutherford and the Nuclear Model
his model called the Rutherford model demonstrated how the nucleus is tiny, but positively charged and heavy; held in the center. Furthermore, he explained how everything is circulating around it with distance, much like the sun and planets orbiting. This model used to show his discovery is called the Nuclear Model. -
Robert Millikan
He created the oil drop experiment which measured the energy of an electron, which at that time, people were still skeptical that there were smaller particles than an atom inside one. -
Niels Bohr - the Bohr Model and the Torodial Model
He proposed the theory that atomic electrons travel in separate circles or orbits around the center-the nucleus- which corresponds to the Bohr Model: this planetary model shows how negatively charged electrons orbit a small, positively charged nucleus, similar to how the planets orbit the sun. Toroidal Ring Model - 1913, Niels Bohr proposed electrons in circular orbit around the nucleus with quantized values of an of angular momentum. -
Louis de Broglie
This french physicist in his 1924 thesis presented his work and studies on the quantum theory, showing that the patterns in which neutrons travel is not regular. -
Werner Heisenberg
Discovered a way to formulate quantum mechanics in terms of matrices. -
Erwin Shrödinger - The Wave Model and The Quantum Model
he elaborated on the bohr’s model by creating equations to predict the locations of the different electrons in an atom. He has also created The Wave Model to show the wave patterns. Wave Model- in 1926, the wave model was created to show that electrons not only travel in orbit around the nucleus, but in a wave pattern or formation. Quantum Model - Schrödinger used mathematical equations to describe the likelihood of finding an electron in a certain position. -
James Chadwick
1932 He proposed the idea for the little particles in an atom that possesses energy or radiation with the mass equivalent to a proton. This was called a neutron. -
Robert Oppenheimer
Robert and his team designed and researched the atomic bomb, and he later was famous for saying “Now, I am become Death, the destroyer of worlds”. The atomic bomb can cause damage through heat, radioactivity, and blasts. -
Joseph Lucas - The Lucas Model
A high school student named Joseph Lucas shared his model of the atom. It is the most successful atomic model ever made. It is a real life model that shows where the electrons around the nucleus are located and shows why there are seven rows on the periodic table. It predicts the position of the nucleus and nuclide spins as well. -
Sources
Live Science, August 28, 2017 https://www.livescience.com/32016-niels-bohr-atomic-theory.html
Universe Today, December 11, 2015 https://www.universetoday.com/60058/democritus-atom/
History Of The Atomic Theory https://historyoftheatomictheory.weebly.com/aristotle.html
Encycolpedia Brittanica https://www.britannica.com/science/Rutherford-atomic-model
