1. The Atom: From Philosophical Idea to Scientific Theory
Section 3.1

2. Defining the Atom- (see p. 43)
The _______philosopher ____________(460 B.C. – 370 B.C.) was among the first to suggest the existence of _________(from the Greek word “atomos”).
He believed that “atoms” were __________ and ________________.
His ideas did agree with later scientific theory, but did not explain __________ _____________. They were ______________ ___________________but just philosophy.

3. Foundations of the Atomic Theory
Better equipment (technology) for the study of matter became available later in history as _____________________ started being conducted.
This lead to the discovery of several ________________________.
There was no real explanation for the laws until ____________proposed his atomic theory.

4. Law of Conservation of Mass
__________________________: mass is neither created nor destroyed during ordinary chemical reactions or physical changes

5. Law of Definite Proportions
_____________________________: chemical compounds contain the same elements in exactly the same proportions by mass, regardless of the size of the sample

6. Law of Multiple Proportions
_________________________: if two or more different compounds are composed of the same two elements, then the ratio of the masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers

7. Visual for Law of Multiple Proportions

8. Dalton John Dalton was a schoolteacher in England around 1800.
He proposed an explanation for the three laws previously mentioned.
He said that elements were composed of ________and only ______________ __________ of atoms could combine to form ____________________.

9. Dalton’s Atomic Theory
1) All matter is composed of extremely small particles called __________
2) Atoms of a __________________ are _________________in size, mass, and other properties; atoms of __________ elements _________in size, mass, and other properties
3) Atoms cannot be _______________, _____________, or ______________

10. Continued
4) Atoms of different elements combine in ___________________ _______ to form __________________.
5) In chemical reactions, atoms are _____________, ______________, or _________________.

11. Modern Atomic Theory
Dalton’s theory was scientific, but not entirely correct.
We now know that atoms are _______ into smaller particles.
A given element can have atoms with _________________masses.
Dalton’s model is called the “_______ __________” or “____________” model.

12. Dalton’s idea of the atom
A Particle Model of the Atom