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400
Democritus
Democritus added on to Leucippus’s Atomic theory (400 BC)
Democritus also said that the shape of an atom was firm and that the atoms are solid, but they floated around in a void.
Democritus also said that the solidness of an object depended on the formation of atoms.
His hypothesis intrigued other “atomists” to think deeper and do more research about what everything was made of. In May, 1911, Ernest Rutherford discovered the nucleus: the hard core of the atom. -
Antoine Lavoisier
Named Oxygen and Hydrogen
French chemist
both named oxygen and hydrogen in 1775
his experiments and accurate measurements of the amounts of substances led to overcome the ancient phlogiston theory
matter cannot be destroyed or created -
John Dalton
Created the Dalton’s Atomic Laws
-John Dalton came with his Atomic theory as a result of his research into gases
-he had discovered that particular gases were only able to be combined in certain proportions, even if two (different) compounds shared the same element group or common element
-started his recording his observations in 1787
-His observations led him to hypothesize that elements combine at the atomic level in fixed ratios -
J.J. Thomson
Discovers the electron
While doing an experiment on electric discharge in a high-vacuum cathode-ray tube, he discovered an electron.
This has helped us understand more about how atoms work because the electrons are the parts of the atoms that do the “cool chemical stuff” (Hank Green).
In 1904, he also proposed a different model of the atom.
Another scientist, once again, proving Democritus’s wrong.
Created the Plum Pudding Model of the atom. -
Marie & Pierre Curie
-Best known for pioneering work in the study of radioactivity
Discovered an unknown radiating element
-Best known for pioneering work in the study of radioactivity
-Their pioneering work had led them to their discovery (in 1898) of the elements radium and polonium
-In 1898 Marie Curie drew the revolutionary conclusion that pitchblende contains a small amount of an unknown radiating element
-atoms were not indivisible and could be broken up -
Max Planck
Formed Quantum Theory
Studied blackbody radiation (1897) and discovers that long wavelengths disobeyed the laws by Wilhelm Wien.
Leads him to announcing Quantum Theory.
Quantum Mechanics has explained the structure of the atom and the structure of the nucleus and without that, most of the physics and chemistry experiments that have been done to this day wouldn’ -
Albert Einstein
Mathematically proves the existence of atoms
Einstein proved atoms existed by first proving Brownian Motion.
Robert Brown first thought of this when he saw a piece of pollen moving around in water even though nothing was touching it.
Einstein proved that particles were pushing the pollen around.
Now people don’t and can’t run around saying “ATOMS ARE JUST A THEORY!”
This has let us understand more about our world and what everything is made of. -
Ernest Rutherford
Created a whole different atomic model
He Tested J.J Thomson's hypothesis by creating his "gold foil" experiment
The Bohr model was built on the Rutherford theory
Rutherford had said that electrons orbited the nucleus very much like the planets around the sun
-1911 created a whole different model
-He also discovered two basic forms of radioactivity in 1908 -
Niels Bohr
Bohr said that electrons orbit around the nuclei (later proved wrong)
Fixed/Improved Rutherford’s modeling problems
Creates Bohr Model of the atom
The Bohr Model makes it easier to explain to people how the atom works and roughly what it looks like.
This has helped us a lot because it’s easy to explain which means you don’t have to be a scientest to understand how an atom works! -
Electron Cloud
Heisenberg -
James Chadwick
Discovered the Neutron
1930 when the alfa particles (helium nuclei) were sent against beryllium strong radiation was emitted
1932 he was able to show a neutral particle that was emitted.
Rutherford had proposed earlier that a neutral particle might exist in nuclei
