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The Atom (John Dalton (1st to put together a model of atomic structure.,…
- The Atom: the smallest part of an element that can enter into a chemical change
- nucleus
- electron cloud / orbital
John Dalton
- 1st to put together a model of atomic structure.
- Dalton's Atomic Theory (1808)
- All matter: made of smaller particles.
- All atoms cannot be broken down into smaller particles.
- Atoms cannot be made / destroyed.
- All atoms of an individual element are identical.
William Crookes (1975)
- Demonstrated that there was some sort of radiation coming from the end of a vacuum tube to the neg. end of a battery.
- Discovery of the Electron
- 1875: Tried to find out what was happening inside the glass tube (vacuum tube).
- Observed: when the gas conducted the electric current, a glow / luminescence appeared in the tube.
- Basically figured out that an electron had a charge -> most likely negative.
JJ Thompson
- Developed a model: the atom, including internal structure.
- Essentially discovered the electron.
- Used Crookes Theory to prove that cathode rays were negatively charged particles.
- Found: electrons are deflected in a magnetic field.
- Thomspon's Plum Pudding Model
- From the results of his experiment: able to calculate the ratio of the charge of the electron to its mass: e/m
- Model: sphere of positively charged material with negatively charged electrons scattered on the inside.
Milikan Oil Drop
- 1909: American physicist set up an experiment to determine the size of the charge of the electron.
- He sprayed tiny droplets of oil between two charged electric plates.
- Used x-rays to ionise the air between the plates.
- Charge of electron: 1.6x10 coulombs.
- MAss of electron: 9.1x10 kg.
- This expt. compounded the relationship: charge and mass.
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- Niels Bohr: Wave mechanical model
- Chadwick (1935) - neutron
- Protons could not exist on their own (pos. repel)
- Had to be something else holding them together.
- Neutrally charged particles: neutrons.
- Erwin Shrodinger - Austrian
- Quantum physics, electrodynamics, general relativity.
- Electrons of probability: cloud is more dense around the atom, electron has more probability of being there.
- Created equation: show shapes of atoms by putting their properties into question.
- Electrons acted in waves rather than particles.
- Werner Heisenberg's Theory of Uncertainty - German
- Employed: Manhatten Project
- Theory of Uncertainty: the position and velocity of an electron can not be measured accurately simultaneously. (Any light touching it would cause it to move in a different velocity as its mass is so small.
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