1. Chemistry Unit: Chapter 3
Atomic Structure

2. Timeline of the Atomic Structure

3. What is the current structure of an atom?

4. What is the current structure of an atom?
Protons
Positive (+) Charge
Located in the nucleus
Do not change in numbers

5. What is the current structure of an atom?
Neutrons
Neutral (0) Charge
Located in the nucleus
Able to change numbers

6. What is the current structure of an atom?
Electrons
Negative (-) Charge
Located in the electron cloud
Able to change numbers

7. What is the current structure of an atom?
**Number of Protons and Electrons equal each other**
In a Neutral Atom
Example:

8. Atomic number It is the number of protons
Every element has a unique atomic number.
Ex.
Carbon / atomic number = 6 / number of protons = ______
Nitrogen / atomic number = 7 / number of protons = ______
Oxygen / atomic number = 8 / number of protons = ______ 6 7 8

9. Atomic mass It is the mass of an atom
Atomic mass = # protons + # neutrons
# neutrons = ___________ - ____________
Ex.
Carbon has an atomic mass of 12 and an atomic number of 6
_____ - _____ = # neutrons = ____
Atomic Mass
Atomic Number 12 6 6

10. Atomic mass It is the mass of an atom
Atomic mass = # protons + # neutrons
# neutrons = ___________ - ____________
Ex.
Bromine has an atomic mass of 80 and an atomic number of 35
_____ - _____ = # neutrons = ____
Atomic Mass
Atomic Number 80 35 45

11. Reading Atomic Number and Atomic Mass on the Periodic Table

12. Isotopes The number of neutrons for an element can vary
Atoms with the same # or protons but different # of neutrons are called isotopes
They are identified by their atomic mass
Ex.
Carbon 12: _____ protons and _____ neutrons
Carbon 13: _____ protons and _____ neutrons
Carbon 14: _____ protons and _____ neutrons 6 6 6 7 6 8