1. 12.1 Atomic Structure

2. Subatomic Particles
Subatomic particles are particles that are inside the atom.
proton
neutron
electron

3. Protons positive charge located in the nucleus (center of the atom)
accounts for the mass of an atom
always the same for atoms of the same element

4. Protons
# of protons = atomic number

5. Check in: How many protons are in the atoms of the following elements?Al
Do the number of protons in an atom ever change?

6. Neutrons neutral charge located in the nucleus
account for the mass of an atom

7. Electrons negative charge located in the electron cloud
account for the volume of the atom

8. Comparing Particles
protons and neutrons are MASSIVE compared to electrons
electrons mass is so small we tend to ignore it
to determine the mass of an atom (mass number)
mass # = protons + neutrons

9. Check-in:
If an atom of oxygen has 8 protons and 7 neutrons, what is its mass?
If an atom of chlorine has a mass number of 36, how many neutrons does it have?

10. Atomic Forces REVIEW: opposites attract likes repel
Protons and Electrons:
opposite charges – attract
attraction holds electrons onto the outside of the atom

11. Atomic Forces
Think: If like repel, then why are the protons together in the nucleus?
The strong force holds protons together in the nucleus.

12. VIDEO: Just How Small is the Atom???

13. Varying Subatomic Particles
PROTONS NEVER CHANGE FOR ATOMS OF THE SAME ELEMENT!
electrons and neutrons, however, CAN change

14. Isotopes
Isotopes are atoms of the same element that have different number of neutrons.
If the number of neutrons change, the mass of the atom changes
mass # = protons + neutrons

15. Ions ions are atoms that have a charge
atoms lose or gain electrons to change the overall charge of the atom