History of Atom Flip Book

• The atom– Picture, parts including charge and location

• Chadwick– Discovered the…

• Rutherford– Gold Foil Experiment

• JJ Thomson– Cathode Ray Tube

• Millikan– Oil Drop experiment

• Dalton– Dalton’s Atomic Theory

• Democritus– His 5 ideas

• Aristotle– Link with nature (Figure 4-1)

History of the atoms1. Matter is composed of empty space through which

atoms move2. Atoms are solid, homogeneous, indestructible,

and indivisible3. Different kinds of atoms have different sizes and

shapes4. Differing properties are due to the size, shape and

movement of atoms5. Changes in matter result from the changes in

groupings of atoms

1. Matter is composed of air, fire, water, and Earth

His popularity allowed his ideas to persist into the 1800’s.

Dalton’s Atomic theory1. All matter is composed of

extremely small particles called atoms

2. All atoms of a given element are identical

3. Atoms can not be created, divided, or destroyed (Law of Conservation of Mass)

4. Different atoms combine in simple whole number ratios to form compounds (Law of Definite Proportions)

5. In a chemical reaction, atoms are separated, combined, or rearranged

Unlike Democritus, Dalton proved his ideas with science experiments.

Subatomic Particles• JJ Thomson

– Found charge to mass ratio of electron

– Proved atoms were divisible into smaller subatomic particles—Big Shock to Science Community

– Cathode Ray Tube– Would later create the

Plum Pudding Model

Subatomic Particles

• Millikan

– Oil drop experiment

– Found the charge of one electron

– Electron charge = 1.602x10-19 coulombs

– Accepted as -1 charge

Subatomic Particles• Ernest Rutherford

– Gold Foil Experiment• Shoot positive particles at gold foil

Subatomic Particles

• Ernest Rutherford– Gold Foil Experiment

• Found that most positive shots went straight through but some bounced back

1. Atom was largely empty space through which electrons moved

2. Atoms contained tiny dense region called a nucleus that contained most of the mass

An atom the size of two football fields would have a nucleus the size of a nickel

Subatomic Particles

• Chadwick– Discovered the

neutrons– Neutrons act to

separate the + protons so that they don’t repel each other

Atom

Smallest particle of an element that retains the properties of the element