Atoms and their structure

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Slide 1

Chapter 4

Atoms and their structure

Slide 2

History of the atom

Not the history of atom, but the idea of the atom.

Original idea Ancient Greece (400 B.C.)

Democritus and Leucippus- Greek philosophers.

Slide 3

History of Atom

Looked at beach

Made of sand

Cut sand - smaller sand

Smallest possible piece?

Atomos - not to be cut

Slide 4

Another Greek

Aristotle - Famous philosopher

All substances are made of 4 elements

Fire - Hot

Air - light

Earth - cool, heavy

Water - wet

Blend these in different proportions to get all substances

Slide 5

Who Was Right?

Did not experiment.

Greeks settled disagreements by argument.

Aristotle was a better debater - He won.

His ideas carried through middle ages.

Alchemists tried to change lead to gold.

Slide 6

Who’s Next?

Late 1700’s - John Dalton- England.

Teacher- summarized results of his experiments and those of others.

Elements substances that can’t be broken down

In Dalton’s Atomic Theory

Combined idea of elements with that of atoms.

Slide 7

Dalton’s Atomic Theory

All matter is made of tiny indivisible particles called atoms.

Atoms of the same element are identical, those of different atoms are different.

Atoms of different elements combine in whole number ratios to form compounds.

Chemical reactions involve the rearrangement of atoms. No new atoms are created or destroyed.

Slide 8

Law of Definite Proportions (#3)

Each compound has a specific ratio of elements.

It is a ratio by mass.

Water is always 8 grams of oxygen for each gram of hydrogen.

Slide 9

Law of Multiple Proportions

If two elements form more than one compound, the ratio of the second element that combines with 1 gram of the first element in each, is a simple whole number.

The ratio of the ratios is a whole number.

Slide 10

What?

Water is 8 grams of oxygen per gram of hydrogen.

Hydrogen peroxide is 16 grams of oxygen per gram of hydrogen.