1. Unit V – Ionic Compounds
General Chemistry
Unit V – Ionic Compounds

2. Periodic Trends Review
Affinity = ATTRACT and HOLD electrons
Increasing Electron Affinity
Increasing Electron Affinity

3. Octet/Duet Rule Review
All atoms want to have a full outer shell of electrons…this makes them STABLE
Octet Rule—Noble gases have full set of valence electrons (8 VE)
Duet Rule—Smaller atoms only need to valence electrons to be stable (H, He, Li, Be, B)
Most atoms don’t have full set of VE to be stable and so they form COMPOUNDS

4. Simple Ions IONS Atoms with a positive or negative charge
Positive charge occurs when atom LOSES electrons

6. Simple Ions IONS Atoms with a positive or negative charge
Negative charge occurs when atom GAINS electrons

7. Simple Ions. Cation: Lose electrons; becomes positive “Plussy Cat”
Usually metals (relate to electron affinity)
“Plussy Cat”

8. Simple Ions. Anion: Gain electrons; becomes negative “Ant-ion”
Usually Nonmetals (relate to electron affinity)
“Ant-ion”

9. Ionic Compounds
Cation + Anion = Ionic Compound Ionic Compounds are NEUTRAL (zero charge). Which means… Total POSITIVE charge = Total NEGATIVE charge. (0) net charge = Electroneutrality.

11. -3 -2 -1 +1 +2 +3

12. Tricks and Tips
Tend to have more than one possible ion charge—see ion charge chart

13. Binary Compounds…Names
Binary compounds are two elements together
Remember…the overall charge of an ionic compound is ZERO

14. Binary Compounds…Names
Rules:
Cation is written and named first.
Borrow names from the elements.
2 or more ions – Roman Numerals indicate charge
Example: Copper: Can be either Copper (II) = Cu2+
OR Copper (III) Cu3+
Anion is written second.
Borrow names from the elements BUT change ending to “-ide”.

15. Example BeS Does the cation have multiple ions? No What is its charge?
Beryllium only has one charge: +2
Beryllium has +2 charge; sulfur has -2 charge, so they simplify out leaving no subscript
(1 x 2+) (1 x 2-) = ZERO
Answer: Beryllium Sulfide

16. Example FeCl3 Does the cation have multiple ions? Yes
Iron has multiple charges: +2 or + 3
Look at the subscript on the ANION (Cl) to help determine iron’s charge
There’s a “3” on the Cl, and Cl has a -1 charge, the charge on iron must be Fe3+
Reason: (1 x 3+) (3 x 1-) = ZERO
Since the cation has multiple charges you must include a roman numeral after its name to indicate its charge
Answer: Iron (III) Chloride

17. Practice… NaCl KI CaF2 CuCl2 FeO
Sodium Chloride Potassium Iodide Calcium Fluoride Copper (II) chloride Iron (II) Oxide

18. Binary Compounds…Formulas
Use charges of elements to determine subscripts
Again, remember the overall charge on the compound must be zero, so the total negative charge must equal the total positive charge

19. Writing Formulas…Rules
Write the symbol for the cation, including the charge
If it’s a multiple-charge ion, use the roman numeral provided to determine its charge
Write the formula for the anion, including the charge
Use the elements’ formulas and “swap” the charges to go with the opposite element: these now become subscripts on the opposite element
If the charges are the same, they “cancel” each other out—when you write the formula, it will simplify down

20. “Swapping Charges”
When you “swap” charges on ions, this allows you to show how many of each element you need to make the overall charge “neutral”
Example: Sodium Chloride
Sodium = +1 charge
Chlorine = -1 charge
You only need one of each element to make the compound neutral: (1 x 1+) + (1 x 1-) = 0
NaCl

21. Example Magnesium Oxide Symbols with Charges: Mg2+ O2-
“Swap” the charges—likes cancel each other out
Mg2+ O2-
MgO—like charges cancel out

22. Example Potassium Oxide: K1+ O2-
“Swap” the charges—likes cancel each other out
K1+ O2-
K2O

23. Practice … Lithium Sulfide Calcium Bromide Aluminum Bromide
Lead (II) Sulfide
Iron (III) Oxide
Li2S
CaBr2
AlBr3
PbS
Fe2O3

25. Polyatomic Ions
Ions which consist of two or more atoms that act as a single ion.
Oxyanion: Negative charged polyatomic ion that contains oxygen
Follows same rules as ionic compounds, except you don’t change anion ending
See Polyatomic Ion table

26. Practice… Potassium Hydroxide Silver Sulfide Ammonium Chloride
Beryllium Nitrate
Potassium chlorate
BaSO4
Na2CO3
HgBr2
Cu(NO3)2
Mg3(PO4)2
KOH
Ag2S
NH4Cl
Be(NO3)2
KClO3
Barium Sulfate
Sodium Carbonate
Mercury (II) Bromide
Copper (II) Nitrate
Magnesium Phosphate