1. Matter and Atomic Structure
Chapter 2

2. What Are Elements?

3. Elements All matter is made of elements
Element - a substance that cannot be broken down into simpler substances by physical or chemical means
What are some examples?
Gold
How many are there?
92 naturally occuring

4. Elements Identified with 1, 2, or 3 letter symbols Examples:
Oxygen - O
Sodium - Na
Unununium - Uuu

5. Elements are Made of Atoms
Each element has its own characteristics.
Atom - smallest particle of an element that has all the characteristics of that element

6. Elements are Made of Atoms
Atoms consist of a nucleus with:
Protons - (p+); has mass and a positive electrical charge
Neutrons (n0); same mass as a proton and NO electrical charge
Surrounding atoms are:
Electrons - (e-); has little mass and a negative charge

7. Atomic Number
Atomic Number - The number of protons in an atom’s nucleus
Oxygen has 8 protons, so its atomic number is 8
Carbon has 6 protons, what’s the atomic number?
Molybdenum’s atomic number is 42, how many protons?

8. Atomic Mass Atomic Mass - protons + neutrons
Uranium - 92 protons and 146 neutrons
Mass number = = 238
Silver (Ag) has an atomic mass of 107 and an atomic number of 47. How many neutrons does it have? 60