1. Atomic Structure

2. Atomic Structure
Nucleus
Protons
Neutrons
Electrons

3. Atomic Structure Electrons
Tiny, very light particles (9.11 x g)
Have a negative electrical charge (-)
Move around the outside of the nucleus

4. Atomic Structure Protons Much larger and heavier than electrons
mass is x g
Protons have a positive charge (+)
Located in the nucleus of the atom 

5. Atomic Structure Neutrons Large and heavy like protons
mass is x g
Neutrons have no electrical charge
Located in the nucleus of the atom 

6. Atomic Structure

7. Describing Atoms Atomic Number = number of protons
In a neutral atom, the # of protons = the # of electrons
Atomic Mass= the number of protons + the number of neutrons

8. Ions An atom that carries an electrical charge is called an ion
If the atom loses electrons, the atom becomes positively charged (because the number of positively charged protons will be more the number of electrons)
If the atom gains electrons, the atom becomes negatively charged (because there are more negative charges than positive)

9. Ions The number of protons does not change in an ion.
The number of neutrons does not change in an ion.
So, both the atomic number and the atomic mass remain the same.

10. Ions
This atom has lost an electron. Now it has one more proton than electron.
One more proton means one more positive charge.
This makes the total charge of the atom POSITIVE.
This atom has gained an electron. Now it has one less proton than electron.
One less proton means one less positive charge.
This makes the total charge of the atom NEGATIVE.

11. Isotopes The number of protons for a given atom never changes.
The number of neutrons can change. 
Two atoms with different numbers of neutrons are called isotopes
Isotopes have the same atomic #
Isotopes have different atomic Mass #’s

12. Isotopes