-
500 BCE
The Alchemists
they began creating experiments and activities with Aristotle's idea about matter. They created a scientific process that was used to discover it.
(https://healthresearchfunding.org/alchemists-atomic-theory-explained/)
(https://www.timetoast.com/timelines/atomic-model-timeline-59589314-06f6-410b-a0c5-8d23f60dfa4d) -
440 BCE
Plato
theorizes that solid forms of matter are composed of indivisible elements shaped like triangles
(https://www.thecollector.com/ancient-greeks-discover-atoms-atomism/) -
430 BCE
Democritus
Believed atoms were uniform, solid, hard, incompressible, and indestructible. As well as that they moved in infinite numbers through empty space until stopped.
(https://www.britannica.com/science/atom/Development-of-atomic-theory) -
Robert Boyle
He believed that everything is composed of very tiny particles, atomism
(https://study.com/learn/lesson/robert-boyle-discovery-inventions.html#:~:text=He%20believed%20that%20everything%20was,and%20behavior%20of%20these%20corpuscles.) -
Antoine Lavoisier
Defined that matter was composed of atoms that were not created or destroyed during chemical reactions.
(https://study.com/learn/lesson/antoine-lavoisier-atomic-theory-model.html#:~:text=a%20chemical%20change.-,Antoine%20Lavoisier%20and%20Atomic%20Theory,or%20destroyed%20during%20chemical%20reactions.) -
Billiard Ball Model
An atom model proposed by John Dalton
(https://homework.study.com/explanation/what-is-the-billiard-ball-model.html) -
John Dalton
He made a theory that says all matter is made of atoms, which are invisible, all atoms of a given element are identical in mass and properties, and compounds are combinations of 2 or more different types of elements.
(https://www.khanacademy.org/science/chemistry/electronic-structure-of-atoms/history-of-atomic-structure/a/daltons-atomic-theory-version-2#:~:text=The%20first%20part%20of%20his,more%20different%20types%20of%20atoms.) -
Amedeo Avogadro
that equals volumes of gases at the temperature and pressure contain the same number of molecules regardless of their chemical nature and physical properties
(https://www.uky.edu/~garose/avogadro#:~:text=avogadro&text=A%20principle%20stated%20in%201811,is%206.023%20X%201023.) -
Dmitri Mendeleev
elements arranged according to the value of their atomic weight present a clear periodicity of properties
(https://www.britannica.com/biography/Dmitri-Mendeleev) -
Marie and Pierre Curie
She suggested that the powerful rays, or energy, the polonium and radium gave off were actually particles from tiny atoms that were disintegrating inside the elements.
(https://www.khanacademy.org/humanities/big-history-project/stars-and-elements/knowing-stars-elements/a/marie-curie#:~:text=She%20suggested%20that%20the%20powerful,atoms%20were%20solid%20and%20unchanging.) -
Albert Einstein
He mathematically proved the existence of atoms.
(https://www.ans.org/news/article-969/albert-einstein-and-the-most-elemental-atomic-theory/#:~:text=Einstein%20also%20in%201905%20mathematically,use%20of%20statistics%20and%20probability.&text=Atomic%20theory%20says%20that%20any,always%20in%20random%2C%20ceaseless%20motion.) -
Robert Millikan
His work demonstrated that electrons did have a discrete quantifiable charge
(https://study.com/learn/lesson/robert-millikan-biography-atomic-theory.html#:~:text=Robert%20Millikan%20Atomic%20Theory,-Robert%20Millikan's%20work&text=Millikan's%20work%20demonstrated%20that%20electrons,electron%20could%20also%20be%20calculated.) -
Ernest Ruthford
He described the atom as having a tiny, dense, and positively charged core called the nucleus.
(https://www.primaryconnections.org.au/themes/custom/connections/assets/SBR/data/Chem/sub/atom2/atom2.htm#:~:text=In%201911%2C%20Rutherford%20described%20the,planets%20revolving%20around%20the%20Sun.) -
Henry G. J. Mosely
the square root of the frequency of the X-ray emitted by an atom is proportional to its atomic number.
(https://study.com/academy/lesson/henry-moseley-biography-atomic-theory.html#:~:text=Moseley%20formulated%20his%20law%2C%20Moseley's,proportional%20to%20its%20atomic%20number.) -
Solar System Model
describes atoms as consisting of a nucleus with a number of electrons in orbits around that nucleus
(https://www.school-for-champions.com/science/atoms_solar_systems.htm#:~:text=The%20Bohr%20model%E2%80%94or%20solar,are%20like%20tiny%20solar%20systems.) -
Neils Bohr
Made the Bohr Model, which had a set number of allowed values of electrons.
(https://www.britannica.com/science/Bohr-model) -
Electron Cloud Model
A wave-like behavior of an electrons in an atom
(https://en.wikipedia.org/wiki/Atomic_orbital) -
James Chadwick
-
JJ Thomson
He discovered that all atoms contain tiny negatively charged subatomic particles or electrons
(https://www.khanacademy.org/science/chemistry/electronic-structure-of-atoms/history-of-atomic-structure/a/discovery-of-the-electron-and-nucleus#:~:text=J.J.-,Thomson's%20experiments%20with%20cathode%20ray%20tubes%20showed%20that%20all%20atoms,positively%2Dcharged%20%22soup.%22)