Chp. 4

What did Aristotle study/do.
Politics, ethics, nature, physics, and astronomy.
Name 3 things that make up an atom, their charges, and the abbreviation.
Proton = p+ (1+) positive

Electron = e- (1-) negative

Neutron = n(little o) neutral

Define Atom.
The smallest part of any element that retains the properties of that element.
What did William Crooke do to find a negatively charged particle? And how does it work?
He created the Cathode Ray. There is a tube with cathode and anode in it. Then there is pressured gas inside. The ends are attached to a voltage source.
Who was the “true” founder of an electron. What was his model for an atom.
J.J Thompson. He thought of the plum-pudding model. Where the electrons just float around.
What where Democritus thoughts about and atom?
1. Matter has empty space and atoms are moving.

2. Atoms are solid, homogenous, indivisible, and indestructible.

3. Different shape and sizes of atoms.

4. Properties= size, shape, movement of atoms.

5. Changes are from grouping of atoms, not changing them.

What did John Dalton think about the atom?
1. All matter is composed of small particles called atoms.

2. Atoms of a given element are identical= size, mass, chemical properties. Atoms of different elements are different.

3. Atoms cannot be created, destroyed, and cannot be divided.

4. Atoms of different elements form compounds in small whole number ratios.

5. chemical reaction= atoms are seperated combined, or rearranged.

Robert Millikan came up with the official of the electron what was it?
Ernest Rutherford modified the plum pudding model. Describe it.
There are alpha particles that move through the atoms and slightly bump off of electrons and change direction.
Ernest Rutherford changed his modified plum pudding model in 1911 describe this new model.
There is a nucleus with positive protons in it. Electrons are outside the nucleus and alpha particles move through the atom and bounce off the electrons and change direction.
Who did the Gold Foil experiment?
Ernest Rutherford
What did James Chadwick find out?
There are neutrons they are neutral particles and have a mass.
Who found the:




Proton= Rutherford

Electron=J.J Thomson

Nucleus= Chadwick

What did people believe in before the idea of an atom?
hot wet
Fire Water
dry cold