1. CHEMISTRY PART 4 Reactivity and Ions

2. Reactivity  Atoms want to be stable.  Want a full valence shell.  Want to be like the nearest Nobel Gas  The Nobel Gases are very stable.  Unreactive.

3. Think about it...  Which group of elements would be the most reactive?  Metals  alkali (1 valence e-)  Non-metals  halogens (7 valence e-)

4. Reactivity Example  Sodium  Na  11 electrons  Group 1  1 valence e-  How can Sodium be like the nearest Nobel Gas?  Add 7 to be like Ar  Lose 1 to be like He

6. Reactivity Example  Sodium will lose its 1 valence e-.  This is easier.  The shell will no longer exist.  Na will now have 10e- on two shells like Ne  Na now has 11p+ and 10e-  It now has a +1 charge.

7. Reactivity Example  How can S become stable?  Group 16  6 valence e-  Gain 2e-  S now has 16p+ and 18e-  It now has a -2 charge.

8. Ions  An atom or group of atoms that carries an electric charge.

9. Ions  Cation  A positively (+) charged ion.  Formed by losing electrons.  Almost all metals are cations. Groups 1 and 2.

10. Ions  Anion  A negatively (-) charged ion.  Formed by gaining electrons.  Mostly group 7 (halogens) and group 6.

11. Naming Ions  Cation  Metals  Name is the full atom name.  Sodium ion  Na +

12. Naming Ions  Anion  Non-Metals  Name of atom ends in “ide”.  Chloride ion  Cl -  Oxide ion  O 2-

13. Practice  Worksheet  Page 109 # 4, 9