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The People Behind the Atom
Transcript of The People Behind the Atom
The Scientists Behind the Atom
and one philosopher
lived around 300 BC
he termed the word "atom" meaning indivisible
scientists rely on evidence
there was no evidence of atoms until the 1700s
Democritus was a philosopher and not a scientist
English chemist, meteorologist, and physicist
determined the molecular formula for water
1. All matter is made up of tiny indivisible particles called atoms
2. Atoms of different elements are different and atoms of the same element are identical
3. Atoms of one element cannot be changed to atoms of another element
4. Atoms can combine chemically or physically
5. Atoms combine to form compounds in specific whole number ratios
Dalton's Atomic Theory
Atoms can be divided and combined through nuclear reactions which create nuclear energy.
Dalton's Atomic Theory is Wrong
Atoms of the same element can have different numbers of neutrons and hence having different masses and characteristics
Atoms can be changed into different atoms through nuclear reactions and by the process of radiation
conducted experiments with a cathode ray tube
concluded that the cathode ray tube is made of smaller particles than atoms
named the smaller particles electrons
Negatively charged particles called electrons float around in a positively charge mass
JJ Thomson's Plum Pudding Model
so do chocolate chip cookies
Plum pudding looks like this.
discovered nucleus through the gold foil experiment
shot helium particles at a piece of gold foil
most of the helium particles went straight through the foil
concluded that most of the atom is empty space, with a dense positively charged mass
claimed that electrons were in energy levels around the nucleus
decided electrons orbit nucleus
a beam of particles was produced, but the beam had no charge
fired helium atoms at a sheet of beryllium
particles called "neutrons"
came up with the billiard ball model of the atom
came up with the electron cloud model of the atom
electrons in a "cloud" around the nucleus
protons and neutrons in the nucleus
This was termed the nuclear model of the atom
Robert A. Millikan
discovered the mass-charge ratio of the electron
with Henry Fletcher
Oil Drop Experiment