1. The Atom What defines the property of a substance

2. WHAT MAKES UP MATTER?  The one thing that makes up all things in the universe is: ATOMS

3. WHAT ARE ATOMS?  Atom: smallest part of an element that can be identified as the element. (can be found on periodic table)  For instance water (H 2 O), it can be broken down to 2 hydrogen atoms and 1 oxygen atom.

4. DEMOCRITUS

5.  Democritus: the first person to suggest the idea of atoms.  He was a Greek philosopher who lived more than 2400 years ago.  He used the word “atom” which means cannot be divided.

6. JOHN DALTON

7. DALTON’S ATOMIC THEORY  In the early 1800’s, stated an atomic theory of matter.  Dalton’s theory was the beginning of the modern theory of atoms.

8. DALTON’S ATOMIC THEORY All elements are composed of atoms. Atoms cannot be divided or destroyed. Atoms of the same element are exactly alike. Atoms of different elements are different. The atoms of 2 or more elements can join together to form compounds.

9. TODAY  We know that atoms define the chemical properties of different substances  Atoms can be divided into smaller particles  These particles help to define the characteristics of the atom

10. PARTS OF THE ATOM  Electron: negatively charged particle.  Neutron: neutral particle.  Proton: positively charged particle.  Nucleus: center, or core, of an atom.

11. PARTICLES OF THE ATOM  Proton:  Mass: 1.673 x 10 -24 g  Atomic mass: 1  Charge: +1  Location: Nucleus

12. PARTICLES OF THE ATOM  Neutron:  Mass: 1.675 x 10 -24 g  Atomic mass: 1  Charge: 0  Location: Nucleus

13. PARTICLES OF THE ATOM  Electron:  Mass: 9.11 x 10 -28 g  Atomic mass: 0  Charge: -1  Location: Space around the nucleus  The electron is so small compared to the other particles, it is given an atomic mass of 0

14. PARTS OF THE ATOM

15. HOW DO ELECTRONS ORBIT THE NUCLEUS  In your notebook, draw how you think the electrons go around the nucleus  In addition, HOW many elections go in each section?

16. BOHR MODEL  The model most of you suggested is called the Bohr model of the atom  Using the periodic table, you can figure out how many electrons “orbit” in each “shell” of the atom  We will be discussing the “electron configuration” later in the quarter