1. Prentice-Hall Chapter 4.1 Dr. Yager
Atomic Structure
Prentice-Hall Chapter 4.1
Dr. Yager

2. Objectives Describe Democritus’ ideas about atoms
Explain Dalton’s Atomic Theory
Identify what instrument is used to observe individual atoms or molecules.

3. Democritus

4. First “Atom” Theory Greek philosopher Democritus (440 B.C.E.)
The atom is the smallest particle into which matter can be divided.
Atoms are indivisible and indestructible.
“Color exists by convention, sweet by convention, bitter by convention, in reality nothing exists but atoms and the void.”
Limitation: All atoms are the same. No concept of different elements or how to explain chemical behavior.

5. Democritus’ View of an Atom

6. What He Had to Work With:
                                                                              
We had to wait 2,200 years to get to the next theory.

7. Next Theory: Dalton’s Atomic Theory (1803)
John Dalton, English chemist and school teacher
Used experimental methods, not philosophy to create scientific theory
All elements are made of atoms which cannot be created, divided or destroyed.
Same element, same atom; different element, different type of atom
Different atoms can physically mix or chemically join to form compounds.
Chemical reactions occur when atoms are separated, joined or rearranged.

8. Dalton’s View of an Atom

9. Dalton’s View of an Atom

10. Dalton’s View of an Atom

11. Dalton’s View of an Atom

12. Size of an Atom An old penny is made up of copper (Cu)
Each penny has about 2.4 x 1022 atoms
World population about 6 x 109 people
100,000,000 atoms lined up is about 1cm
Atomic radii range 5 x m - 2 x m
Can observe individual atoms with “Scanning Tunneling Microscope”

13. Scanning Tunneling Microscope

14. Iron Atoms Seen Through a Scanning Tunneling Microscope

15. MoS2 Molecules

16. 5 nm Gold nano-particles

17. Plato. Aristotle. Democritus. Socrates.
1. The ancient Greek philosopher credited with suggesting all matter is made of indivisible atoms is
Plato.
Aristotle.
Democritus.
Socrates.

18. Plato. Aristotle. Democritus. Socrates.
1. The ancient Greek philosopher credited with suggesting all matter is made of indivisible atoms is
Plato.
Aristotle.
Democritus.
Socrates.

19. 2. Dalton's atomic theory improved earlier atomic theory by
teaching that all matter is composed of tiny particles called atoms.
theorizing that all atoms of the same element are not identical.
using experimental methods to establish a scientific theory.
not relating atoms to chemical change.

20. 2. Dalton's atomic theory improved earlier atomic theory by
teaching that all matter is composed of tiny particles called atoms.
theorizing that all atoms of the same element are not identical.
using experimental methods to establish a scientific theory.
not relating atoms to chemical change.

21. 3. Individual atoms are observable with
the naked eye.
a magnifying glass.
a light microscope.
a scanning tunneling microscope.

22. 3. Individual atoms are observable with
the naked eye.
a magnifying glass.
a light microscope.
a scanning tunneling microscope.