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501 BCE
The Alchemists
The Alchemist's Atomic Theory was presented by Leucippus the Greek philosopher. Source: https://healthresearchfunding.org/alchemists-atomic-theory-explained/ -
Period: 500 BCE to 600 BCE
The Alchemists
The first atomic theories were introduced around the 6th century BC by Leucippus. He was a Greek philosopher who introduced core ideas to science.
Those Ideas were: That matter could be eternal, as no material thing can come from nothing.
Material things are made from particles that are very small and indivisible.
These small, unseen particles could come in different shapes and sizes.
The particles are in motion continuously. -
Period: 428 BCE to 348 BCE
Plato
Even though Plato's ideas were wrong, an example is that he thought everything was made up of fire, water, earth, and air, yet he did provide the ancient world an idea: The existence of atoms. Source: https://www.slideshare.net/Muthurajnghs/atomic-structurehtml -
400 BCE
Democritus
He was a famous philosopher primarily remembered today for his formulation of an atomic theory of the universe. One of his ideas is that Atoms and the void as the fundamental constituents of the physical world.
Source: https://plato.stanford.edu/entries/democritus/ -
387 BCE
Plato
He was an atomist and was the first to introduce to the world the existence of atoms, even though his theories were widely accepted but wrong. -
Period: 370 BCE to 460 BCE
Democritus
Democritus, known in antiquity as the ‘laughing philosopher’ was one of the two founders of ancient atomist theory. He elaborated a system originated by his teacher Leucippus into a materialist account of the natural world. The atomists held that there are the smallest indivisible bodies from which everything else is composed and that these move about in an infinite void. Of the ancient materialist accounts of the natural world atomism was the most influential. -
Period: to
Robert Boyle
He is recognized as the first chemist and is also famous for his discovery that atoms must exist based on the relationship between pressure and the volume of gas. His theorem called Boyle's law reasons that because a fixed mass of gas can be compressed, gas must be made of particles or atoms because there is space between them.
Source: https://www.reference.com/science-technology/robert-boyle-s-contribution-atomic-theory-2933c73ad42cc70b -
Robert Boyle
He is recognized as the first chemist and is also famous for his discovery that atoms must exist based on the relationship between pressure and the volume of gas.
Source: https://www.reference.com/science-technology/robert-boyle-s-contribution-atomic-theory-2933c73ad42cc70b -
Period: to
Antone Lavoisier
He made and proved The Law of Conservation of Mass, Law of Definite Proportions, and Law of Multiple Proportions. These Laws helped people understand Mass Proportions and Atoms more better -
Period: to
John Dalton
Dalton's atomic theory was the first complete attempt to describe all matter in terms of atoms and their properties.
Dalton based his theory on the law of conservation of mass and the law of constant composition. -
Period: to
Amedeo Avogadro
Amedeo Avogadro was an Italian scientist known for his research on gas volume, pressure, and temperature. He formulated the gas law known as Avogadro's law, which states that all gases, at the same temperature and pressure, have the same number of molecules per volume. Today, Avogadro is considered an important early figure in atomic theory. -
Antoine Lavoisier
He was a nobleman and a famous chemist
who proved and made the law of conservation,
the Law of Definite Proportions, and,
the Law of Multiple Proportions.
Source: https://chem.libretexts.org/
Courses/Rutgers_University/
Chem_160%3A_General_Chemistry/
01%3A_Atoms/1.05%3A_Modern_
Atomic_Theory_and_the_
Laws_That_Led_to_It -
John Dalton
John Dalton was a famous chemist and physicist and was also credited for making the first complete atomic theory to describe all matter in terms of atoms and their properties.
Source: https://www.khanacademy.org/science/chemistry/electronic-structure-of-atoms/history-of-atomic-structure/a/daltons-atomic-theory-version-2 -
John Dalton's Billiard Ball Model
John Dalton developed an atomic theory that all substances are made of atoms, and that atoms are solid, hard spheres like billiard balls. He used wooden balls to model atoms and compounds, and his theory was accepted by many scientists comparing his model with modern models of subatomic particles. -
Amedeo Avogadro
He was an Italian Scientist who made contributions to molecular theory. -
Period: to
Dmitri Mendeleev
Dmitri Mendeleev was a Russian chemist and inventor. He is best known for making the Periodic Law and creating a version of the periodic table of elements. He used the Periodic Law not only to correct the then-accepted properties of some known elements, such as the valence and atomic weight of uranium but also to predict the properties of three elements that were yet to be discovered. The periodic table also introduced Atomic weight and numbers to help people better understand the table. -
Period: to
Sir J. J. Thomson
Sir J. J. Thomson discovered the electron and conducted an experiment with cathodes (negatively charged electrodes) and anodes (positively charged electrodes) in 1896. From this experiment, Thomson hypothesized that atoms need particles with a positive charge to balance the negative charge of electrons to make atoms neutral, and atoms need to have other particles to account for most of their mass since electrons are low in mass.
Source: https://www.britannica.com/science/Thomson-atomic-model -
Period: to
Pierre and Marie Curie
The Curies were studying uranium rays, when they made a claim that the rays were not dependent on the uranium's form, but on its atomic structure. The theory created a new field of study, atomic physics, and Marie herself coined the phrase "radioactivity." She defined radioactivity at the time to be the activity of rays to be dependent on uranium's atomic structure, the number of atoms of uranium. In 1903, Marie Curie and her husband won a Nobel Prize in physics for their work on radioactivity. -
Period: to
Robert A. Millikan
As a scientist, he made many discoveries in physics. His earliest success was the accurate determination of the charge carried by an electron, using the “falling-drop method”; he also proved that this number was a constant for all electrons, thus demonstrating the atomic structure of electricity. His law of motion of a particle falling towards the earth after entering the earth’s atmosphere with his other investigations on electrical physics ultimately led him to his studies of cosmic radiation. -
Dmitri Mendeleev
Dmitri Mendeleev created the first periodic table in 1869 by arranging elements that had similar properties into seven groups. He also published the Periodic Law that stated the properties of elements are periodic functions of their atomic numbers. -
Period: to
Ernest Rutherford
Ernest Rutherford was a famous physicist. An experimentalist, Rutherford was responsible for a remarkable series of discoveries in the fields of radioactivity and nuclear physics. He set forth the laws of radioactive decay and postulated the nuclear structure of the atom: experiments done in Rutherford’s laboratory showed that when alpha particles are fired into gas atoms, a few are violently deflected, which implies a dense, positively charged central region containing most of the atomic mass. -
Period: to
Albert Einstein
Albert Einstein worked extensively in the field of theoretical physics. He also published papers concerning the nature of light that became a cornerstone of the quantum theory such as the Photoelectric Effect (many metals emit electrons when light is shined upon them) lastly, he put forth more analysis into the aspects of molecular motion and the particle theory.
Source: https://www.biography.com/scientists/albert-einstein -
Period: to
Neils Bohr
Niels Bohr was an accomplished physicist who came up with a revolutionary theory on atomic structures and radiation emission. He then discovered that Atoms give off electromagnetic radiation as a result of electrons jumping to different orbit levels He won the 1922 Nobel Prize in physics for another idea, The concept asserted that physical properties on an atomic level would be viewed differently depending on experimental parameters. -
Period: to
Henry G. J. Mosely
He was a famous physicist who experimentally demonstrated that the major properties of an element are determined by the atomic number, not by the atomic weight, and firmly established the relationship between atomic number and the charge of the atomic nucleus. -
Period: to
James Chadwick
James Chadwick was an English physicist who received the Nobel Prize for Physics in 1935 for the discovery of the neutron. In the process, he and Rutherford studied the transmutation of elements by bombarding them with alpha particles and investigated the nature of the atomic nucleus, identifying the proton, the nucleus of the hydrogen atom, as a constituent of the nuclei of other atoms. -
Sir J. J. Thomson
He is a famous physicist who is credited with the discovery of the electron and the need for an atom to have a positive and negative charge to work.
Source: https://www.britannica.com/science/Thomson-atomic-model -
J. J. Thomson's Plum Pudding Model
The plum pudding model is one of several historical scientific models of the atom. First made by J. J. Thomson in 1904, the model tried to account for two properties of atoms then known: the electrons that are negatively charged subatomic particles and the atoms that have no net electric charge. The plum pudding model has electrons surrounded by a volume of positive charge, like negatively charged "plums" embedded in a positively charged "pudding". -
Ernest Rutherford
Ernest Rutherford was an experimentalist and a famous physicist. He also figured out the nuclear structure of an atom. -
Pierre and Marie Curie
They were husband and wife and they conducted pioneering research on radioactivity. Later they won a Nobel Prize in two fields in Science. -
Albert Einstein
He was a famous Physicist who won the Nobel Peace Prize for physics and proposed that electromagnetic radiation was quantized and made up of a stream of particles
Source: https://www.biography.com/scientists/albert-einstein -
Robert A. Millikan
Robert Millikan, a famous physicist conducted an Oil Drop experiment to determine the charge and mass of an electron. -
Neils Bohr
He is a famous Physicist and Bohr’s own research led him to theorize in a series of articles that atoms give off electromagnetic radiation. His ideas then formed the basis of future atomic research.
Source: https://www.biography.com/scientist/niels-bohr -
Henry G. J. Mosely
He was a famous physicist who demonstrated that the properties of an element depend on the atomic nucleus -
Neils Bohr's "Atoms with orbits", Solar System Model
Bohr's model suggests that the atomic array of atoms are produced by electrons gaining energy from some source, jumping up to a higher energy level, and then immediately dropping back to a lower energy level and emitting the energy difference between the two energy levels. This suggests the idea of " Atoms With Orbits" The existence of the atomic array supports Bohr's model of the atom. -
Erwin Schrondinger's Electron Cloud Model
An Electron Cloud Model in atomic theory is an atomic orbital function describing the location and wavelike behavior of an electron in an atom. -
James Chadwick
He was a famous physicist and is famous for his finding of the neutron.