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

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

Charges

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

LIKE CHARGES REPEL

Like Charges Repel Like Charges Repel

Unlike Charges Attract

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

Parts of an Atom Protons Positive Neutrons Neutral Electrons Negative

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

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

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

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

Remember, we only transfer and accept electrons Electrons

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

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

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

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-

Common Ions Pg. 33 in the blue book

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

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