Happy New Year!!!

1. Happy New Year!!! Remember the old year?

2. Remember??? • All atoms “want” to have stable electron configurations like the noble gases. • Most of the noble gases have 8 valence electrons (except Helium). • What’s the name of this rule that atoms want 8 valence electrons (usually)? • The Octet Rule!!!

3. Remember??? • Metals lose electrons to follow the octet rule. • What is the charge on a metal ion that has lost electrons? • Positive • What is the name for an ion with a positive charge? • Cation • Is the cation the “first name” or “last name” when naming a compound? • First name • How is the cation name different from the element’s name? • It’s the same

4. Remember??? • Non-metals gain electrons to follow the octet rule. • What is the charge on a non-metal ion that has gained electrons? • Negative • What is the name for an ion with a negative charge? • Anion • Is the anion the “first name” or “last name” when naming a compound? • Last name • How is the anion name different from the element’s name? • The ending is changed to “ide.”

5. Remember??? • To determine valence electrons, just use the group number.

6. Some practice

7. Remember??? Chlorine needs to gain an electron Sodium needs to lose an electron • Ionic compounds form when metal and non-metal ions give and take electrons, are attracted, and stick together due to their opposite charges. The sodium and chlorine are oppositely charged and opposites attract!

8. Remember??? • Chemical Formulas • Symbols tell the elements in the compound • Subscripts tell the number of atoms of each element. • No subscript means that there is one atom of the element. • C2H6 6 hydrogen atoms 2 carbon atoms

9. Remember??? • In ionic compounds, the charges must balance out. • If calcium ionically bonds with fluorine, calcium is giving up 2 electrons but each fluorine atom only needs 1…so you have to have 2 fluorine atoms for every calcium atom. • Ca+2 + F-1 = CaF2

10. Remember??? • The easy way to determine chemical formulas for ionic compounds is the crossover method. • For Aluminum and Oxygen • Write the cation and anion and their charges. Al+3 O-2 • Cross the charges over and down (without the signs). Al+3 O-2 • You have the correct formula! Al2O3 2 Aluminum atoms each gave up 3 electrons for a total of 6 given 3 Oxygen atoms each took 2 electrons for a total of 6 taken • Remember to reduce subscripts if divisible by the same number • Ex. C2O4 reduces to CO2 • Lastly, remember you don’t need to write 1’s as subscripts since having the symbol means there is one atom.

11. Practice!

12. Remember??? • Polyatomic ions • Polyatomic ions are groups of atoms that act together as one ion with one charge. • For example, the nitrate ion (NO3)-1 is made of a nitrogen atom along with 3 oxygen atoms that act together and have an overall charge of -1. • Hydroxide is (OH) -1 • Ammonium is (NH4) +1 • Dichromate is (Cr2O7) -2

13. Remember??? • When writing formulas with polyatomic ions, I recommend keeping the polyatomic ions in parentheses ‘til the end so that you don’t mistakenly change subscripts in the polyatomic ion. • Ammonium oxide • (NH4)+1 O-2 • Crossover: (NH4)+1 O-2 • Formula: (NH4)2O • Lastly, the name of a polyatomic ion does not change when in a compound.

14. Practice!!!