1. Section 3-3
Counting Atoms

2. Three Subatomic Particles:
Charge
Location
Proton +1
Nucleus
Neutron
Electron -1
Electron cloud

3. Atomic Number The number of protons in an atom
Unique for every element

4. Atoms are always electrically neutral
Atoms are always electrically neutral. This means that protons always equal the electron.

5. How many protons & electrons are in the following atoms?
Silicon
Nitrogen
Zinc
14 p & 14 e
7 p & 7 e
30 p & 30 e

6. Mass Number The number of protons and neutrons in the nucleus
Mass Number – Atomic Number = Neutrons

7. How Many Neutrons are in:
Potassium
Argon
Tin
20 n
22 n
69 n

8. Atomic Structure

9. Lithium

10. Phosphorus