Atomic Theory

1
Atomic Theory

• Label the 3 different particles that make up an
  atom
• What is the charge of each?
• Draw a model of the element Boron (B)

2
Development of atomic theory
3
Democritus

• Atoms are indivisible, indestructible,
  fundamental units of matter.
• Atomos
• Never went further than this

4
Aristotle

• Four elements of air, earth, water and fire. 
• Regardless of the number of times you cut a form
  of matter, you would always have a smaller piece
  of that matter. 

5
Daltons Atomic Theory

• 1. All matter is composed of extremely small
  particles called atoms.
• 2. Atoms of given elements are identical in
  size, mass, and other properties.

6
Daltons Atomic Theory

• 3. Atoms can not be subdivided, created, or
  destroyed.
• 4. Atoms of different elements can combine in
  simple, whole-number ratios to form chemical
  compounds.

7
Daltons Atomic Theory

• 5. In a chemical reaction, atoms are combined,
  separated, or rearranged.
• Example
• H2 O2 ? H20

8
William Crookes

• Discovered cathode rays
• Set the stage for JJ Thompson and
  his discoveries

9
J. J. Thomson

• Discovery of the electron
• Cathode ray tube

10

• Positively charged ions, called cations, move
  towards the cathode
• Negatively charged ions, called anions, move
  towards the anode.

11
J. J. Thomsons Model
12

• Robert Millikan -
• oil drop experiment
• - calculated the mass of the electron

13
Ernest Rutherford

• Existence of the nucleus and its relative size
• Gold foil experiment

14
Rutherfords Gold Foil Experiment
15
Rutherfords Gold Foil Experiment
16
James Chadwick

• Discovered the last known subatomic particle
• The neutron which has no charge

17
No. Not this Neutron
This neutron.