Unit V – Ionic Compounds General Chemistry Unit V – Ionic Compounds

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

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

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

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

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

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

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

-3 -2 -1 +1 +2 +3

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

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

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”.

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

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

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

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

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

“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

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

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

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

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

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