1. Remember chemical reactions?
Well turns out there is this concept called The Law of Conservation of Mass.
The Law of Conservation of Mass says the total mass before the chemical reaction is the same as the total mass after the chemical reaction
Reactants = Products

2. Law of Conservation of Mass Practice
Handout – “Understanding Chemical Reactions” balanced and unbalanced section
Then work on the back!

3. Charges

4. Who wants to volunteer? We will rub both balloons against your hair
The balloons repel each other but attract your hair – why?

5. LIKE CHARGES REPEL

6. Like Charges Repel
Like Charges Repel

7. Unlike Charges Attract

8. So What Causes Positive and Negative Charges?
Well, it all comes down to atoms
The charge or lack of charge of an atom comes down to it’s protons, neutrons, and electrons

9. Parts of an Atom
Protons Positive
Neutrons Neutral
Electrons Negative

10. Electrically Neutral Atoms (uncharged)
Atoms that have equal numbers of positively and negatively charged particles
So equal number of protons (positive) and electrons (negative)
Neutrons are neutral so we don’t really care how many of those there are

11. Electrically Charged Atoms
Positive-negative attractions between the protons in one atom and the electrons in another atom
This bond is glue that holds atoms together

12. Ions Charged atoms Atoms can gain electrons – negative ions
or lose electrons – positive ions
negative ion
positive ion
Ionic Bond

13. Ionic Compounds Composed of positive and negative ions
An ionic compound has no net electrical charge
It is neutral because the positive and negative charges balance each other

14. Remember, we only transfer
and accept electrons
Electrons

15. So Remember Atoms Are Positive Or Negative?
Atoms can gain electrons – negative ions
These are Anions
or lose electrons – positive ions
These are Cations

16. So How Do We Get Anions? By gaining electrons from another atom
Remember, anions are negative!
Anion
Cation e-
Ionic Bond

17. So How Do We Get Cations? By losing electrons to another atom
Remember, Cations are Positive!
Anion
Cation e-
Ionic Bond

18. carbonate CO32- acetate - C2H3O2-
Multiple Ions
An ion consisting of a group of 2 or more bonded atoms is called a polyatomic ion
carbonate CO32-
hydroxide - OH-
acetate - C2H3O2-

19. Common Ions
Pg. 33 in the
blue book

20. Writing Chemical Formulas
You can easily write formulas for ionic compounds by following two simple rules:
Write the cation first, then the anion
2) Simplified formula to the fewest positive and negative ions needed to make the total electrical charge = 0
-Basically you have to simplify the formula

21. Practice
On the back of your common ions sheet, fill in the chart!