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400 BCE
Democritus Atomic Theory
Started by cutting a rock in smaller and smaller pieces until he could not cut it any more.
Established "atomos" as the smallest form of matter.
His atomic model was just a sphere of the element that united with other spheres to form the big piece.
MAIN CONTRIBUTION: he established that there were smaller pieces called atoms.
WRONG: his atomic model was a complete particle made up by the element, just like a sphere of the material that got together to make bigger pieces of the same element. -
John Dalton Atomic Theory.
Proposed the Atomic Theory.
Proposed that all matter was composed of atoms, indivisible and indestructible building blocks.
MAIN CONTRIBUTION: his atomic theory is still the base of the atomic information provided by scientists.
WRONG; his atomic model, as well as Democritus model was just a sphere of the element that joined other spheres to form the bigger piece of the element. -
JJ Thomson Atomic Theory
When studying the atom under a microscope he found streams of particles around the atom that he thought were the only matter in the atom.
Suggested that the atom was sphere shaped.
MAIN CONTRIBUTION: His atomic model was the base for the discovery of the negativley charged subatomic particle called "electron" which was first called "corpuscles".
WRONG: because he assumed that the positive charge of an atom was all one uniform blob of matter with the electrons moving in orbits inside the nucleus. -
Ernest Rutherford Atomic Theory.
His experiment consisted in shooting radioactive beams through a minutely thin gold foil and register them in screens coated with zinc sulfide.
He stated that approximately 1 in 8000 of the particles is deflected.
MAIN CONTRIBUTION: he stated that the atom had a positive nucleus surrounded by negaitvely charged orbiting electrons.HIs model was also the bas for the posterior discovery of the nucleus.
WRONG: he did not account all the properties of electrons, by expecting a stable atom. -
Niels Bohr Atomic Model.
By creating the Bohr model he proved that electrons orbit around the positively charged nucleus of protons and neutrons.
He discovered how the particles in atoms relate to each other.
MAIN CONTRIBUTION: he discovered that electrons in atoms are arranged in energy levels.
WRONG: breaks down when applied to multi-electron atoms. It does not account for sublevels (s,p,d,f), orbitals or elecrtron spin. it works very well for atoms with only one electron, but not at all for multi-electron atoms. -
James Chadwick Atomic Model.
He used sacttering data to calculate the mass of the neutral particle.
He saw that the atomic number was less than the atomic mass.
MAIN CONTRIBUTION: he discovered the neutron in the atomic nucleus, he saw aditional mass besides the protons and the electrons so he discovered the nucleus.
WRONG: There are no recorded mistakes for this model yet. -
Erwin Schrödinger Atomic Theory.
Used mathematicl equations to describe the likehood of finfing an electron in a certai position in atomic theory.
Theory used to predict th odds of the location of the electron.
MAIN CONTRIBUTION: he created "The Schrödinger Equation" , in which, he gave a "derivation" for the wave equation for time-independent systems and showed that it gave the correct values for a hydrogen-like atom.
WRONG: this is the actual atomic model used, there are no registered mistakes for this model yet.
