History of the Atomic Model Flashcards
Who was the founder of the Atom and how did he discover it?
The atom was found by Democritus in 440BCE. He discussed what happens if you take something and keep breaking it into something smaller. He stated that if you keep breaking down the object you would get to something that can no longer be broken down.
Who was John Dalton and what did he do? (hint atoms and elements)
In 1808 John dalton showed that common substances always broke down into the same elements in the same proportions.
- Stuff can be broken into elements (the things listed on the periodic table).
- Elements are atoms with different masses.
- Compounds are a combination of elements. You know, like water, salt or pizza.
Who was J.J Thompson and what did he discover? (hint electrons)
In 1897 J.J. Thompson discovered the electron which further advanced that atom theory. He showed the atom as uniformly packed spheres of positive matter filled with negatively charged electrons.
Who was Ernest Rutherford and what did he discover?
Enerest Rutherford took the previous model of the atoms and proved it wrong. He shot small positively charged alpha particles at a sheet of gold foil. While some alpha particles went through the gold foils others deflected. Rutherford concluded that atoms consisted largely of empty space with just a few electrons while most of the mass was concentrated in the center which he determined was the nucleus of the atom. The alpha particles passed through the gaps of the atom but bounced back when they hit the positively charged nucleus.
Who was Neils Bohr and what did he discover?
In 1913 Niels Bohr discovered that electrons orbit the nucleus at fixed energies and distances and are able to jump from one level to another but not to exist in the space between. This theory was further developed to electrons traveling in waves instead of being confined to a particular point in space. He experimented with light going through different mediums like hydrogen gas.
Who was Werner Heisenberg and what did he disvoer?
Werner Heisenberg then formulated the uncertainty principle and showed it was impossible to determine both the exact position and speed of electrons as they moved around an atom.
