1. Atomic Structure: Isotopes and Ions

2. 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

3. Isotopes

4. Ions  An atom that carries an electrical charge is called an ion  If the atom loses electrons, the atom becomes positively charged.  If the atom gains electrons, the atom becomes negatively charged

5. 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.

6. Example 1: Ca +2

7. Example 2: O -2

8. PEN Method for---  Li +1  Cl -1  U-238  Mg +2  F -1  S -2