1. Unit 2 Atomic Structure and Matter

2. Matter and Atoms Matter describes anything that has mass and volume
Can matter be invisible? YES
Ex. Air

3. History of atoms Democritus Was a Greek philosopher in 400 BC
Thought the universe was made of atoms and empty space
ATOM comes from the Greek word atomos, which means cannot be divided

4. Antoine Lavoisier Was a French chemist in the late 1700’s
Lavoisier proved that matter cannot be created or destroyed during chemical changes like burning or rusting
The principle is called The Law of Conservation of Matter

5. Joseph Proust Was a French chemist
He stated that the basic building blocks of a substance are always in the same way
For example every molecule of water is made of 2 hydrogen atoms and 1oxygen atom (H2O)

6. Models of the Atom What is a model?
A model is anything that lets you create an image in your mind of something that is too big, too small or too complex to understand otherwise
Models can also be used to study events that happen too fast or too slow or would be too dangerous to study otherwise

7. John Dalton’s Atomic Model
Dalton was an English chemist
In 1803, he proposed that atoms of the same element are the same and atoms of different elements are different
For example, a piece of lead is made up of only lead atoms
He also stated that atoms are the smallest particle of matter.

8. Atomic Models Atoms are too small to see with the human eye
We need models to help us understand what they look like
Models are not completely accurate. They represent something that is not easily seen or understood

9. Atomic Structure The Nucleus
Is the center of the atom
99.9% of an atom’s mass is in the nucleus
The nucleus is made of protons and neutrons
Protons have a positive charge
Neutrons have no charge
What charge does the nucleus have?
Positive

10. The Electron Cloud
Around the nucleus the electrons fly around in random patterns
An electron has an negative charge
An atom has equal numbers of protons and electrons

11. Electron Cloud
An electron is about times lighter than a proton or a neutron
Electrons can easily be lost because they are far away from the nucleus.
Have you ever rubbed a balloon on your head? Have you ever zapped your little brother?