A Summary of Sections:

4.1: Early Ideas About Matter4.2: Defining The Atom

In chapter 3, we discussed matter. What is the definition of matter?

But – what is matter?

And why should you

care?

Here’s one example: For thousands of years, it was believed that all matter was made of 4 things:

1. __________________

2. __________________

3. __________________

4. __________________This belief was based on philosophy – not scientific experimentation.

One corollary of this belief was

that

______________was thought to

be a good medical

treatment!!

In the early 1800’s John Dalton developed a theory of matter that was the first one to be based on ____________________

____________________ He said all matter was made of _____________

John Dalton is known as the

________________

________________,although he didn’t get everything right…For example, he hypothesized that atoms were

J.J. Thomson discovered the _______________ Why was it so important?

How did he know that there had to be positive charge in the atoms?

In 1911, Ernest Rutherford decided to test the Plum Pudding Model. To do so, he created one of the most important experiments of all time:

the _______________________Experiment.

He shot _____________________ at a thin

sheet of ____________________ and observed

According to the Plum Pudding Model, the

alpha particles would be__________________. What actually happened?

Rutherford said “It was as if you fired a heavy artillery shell at a piece of tissue paper, and it came back and hit you!”

The fact that 1 in 20,000 alpha particles bounced back meant they had to be hitting something very _____________ and very__________. He named it the __________

Where is most of the mass of the atom?

How much mass would a nucleus the size of a period have?

In an atom that is the size of Camden Yards – how big would the nucleus be?

What is the charge on the nucleus? How do you know?

This is a charged particle, surrounded by its electric field.

What surrounds the tiny nucleus?

How do we know that?

What is Rutherford’s model of the atom called?

What keep the electrons from flying away from the nucleus?

Properties of the 3 major subatomic particles

Particle Symbol Location ElectricCharge

~Mass ina.m.u.s

We have come along way since the atom was “discovered.” Now, we can “see” individual atoms, using a

One practical use for all of this is the exciting new field of

Artist’s conception of the future: Two nanobots in pulmonary alveola killing a virus using nano-lasers.

In our quest this year to

understand how our world works

through chemistry, we

start in the world of the very small….The world ofTHE ATOM!