1. Chapter 4 Table of Contents Section 1 Development of the Atomic Theory
Atoms
Table of Contents
Section 1 Development of the Atomic Theory
Section 2 The Atom

2. Section 1 Development of the Atomic Theory
Chapter 4
Objectives
Describe some of the experiments that led to the current atomic theory.
Compare the different models of the atom.
Explain how the atomic theory has changed as scientists have discovered new information about the atom.

3. The Beginning of the Atomic Theory
Section 1 Development of the Atomic Theory
Chapter 4
The Beginning of the Atomic Theory
Democritus, a Greek philosopher
Around 440 BCE
thought that you could have a particle that could not be cut.
Called it an atomos.
Aristotle, another Greek philosopher, disagreed
Basis: What holds the atoms together?
Democritus couldn’t answer the question

4. The Beginning of the Atomic Theory, continued
Section 1 Development of the Atomic Theory
Chapter 4
The Beginning of the Atomic Theory, continued
Democritus was right:
Matter is made of particles,
called atoms.
atom is the smallest particle into which an element can be divided and still be the same substance.

5. Dalton’s Atomic Theory Based on Experiments
Section 1 Development of the Atomic Theory
Chapter 4
Dalton’s Atomic Theory Based on Experiments
John Dalton published his atomic theory in 1803.
His theory stated
all substances are made of atoms.
Atoms are small particles that cannot be created, divided, or destroyed.
Atoms of the same element are exactly alike, and atoms of different elements are different.
Atoms join with other atoms to make new substances.
Not Quite Correct

6. Definition of an Atom
The smallest particle of an element that retains the properties of the element
How small?
World population in 2000 was about 6 billion
One penny contains 5 billion times more atoms

7. Only with ‘scanning tunneling microscopes
Can we See Atoms
Only with ‘scanning tunneling microscopes
Nanotechnolgy manipulates individual atoms to make very small devices
Next generation of computers will have wires one or two atoms wide (smaller, less power, less heat)

8. Pictures

9. Pictures