IONIC COMPOUNDS

IONIC COMPOUNDS 1. What are they? Formed when positive metal ions (cations) join to negative non-metal ions (anions) usually in solution. (This means that the ions are aqueous (aq.) – in water!) They can also form at high temperatures in the gaseous state but this is not as common as solution formation. RECALL: Ions are formed when an atom gains or loses e- from their outer orbital to form a more stable charged particle (Octet Rule: pp. 229)

Positive charges= Negative charges 2. Forming Ionic Compounds Ionic compounds are overall neutral (have no charge); that is, the sum of the positive charges (metal ions) must equal the sum of the negative charges (non-metal ions) Positive charges= Negative charges Recall: Metals are e- givers and their ions are positively charged while non- metals are e- takers and their ions are negatively charged. When they meet – they balance out to neutral!

Examples of ionic compounds being formed: eg.: Sodium metal ions reacting with chloride ions in solution eg.: Magnesium ions reacting with bromide ions in solution eg.: Lithium ions reacting with oxide ions It’s all about balancing the charges so the compound ends up neutral!!

Beryllium Oxide : Calcium Nitride : Sodium Oxide : This is called an ionic equation. It shows the ions from which an ionic compound is formed, including the smallest whole number ratio of ions in the compound! You try! Show the Ionic equation for the formation of…   Silver Chloride : Beryllium Oxide : Calcium Nitride : Sodium Oxide :

3. Finding Ionic Compound Formulas!! Find the Formula for… Magnesium Phosphide All we are doing it trying to balance out all the charges to the lowest whole number so that the ionic compound ends up being neutral!! *RECALL… the metal is always written first in the formula!

A short-cut… The “Criss-cross Method” Another way to predict the formula is to “criss- cross” the charge on the metal to produce the number of non-metals required (i.e. the subscript behind the non-metal), and vice versa Mg 2+ P 3- Mg 3 P 2

Now you try: Predict the formula for calcium oxide Calcium is Ca2+ Oxygen is O2– Formula Ca2O2 This is simplified to CaO Ca2+ O-2

Multi-Valent Ions Some transition metals are multivalent, meaning they have more than one ion form. In the name of the compound, Roman Numerals are used following the cation to indicate which ion was used For example: Manganese (II) Bromide

More Practice Questions: Hebden (p. 76) # 99,108, 105, 113, 114,124,127,144, 149, 153, 161

4. Finding Poyatomic Ion Formulas Recall: Polyatomic ions are two or more different atoms chemically combined and acting like a single charged particle (ion).   Eg.: Eg.: Sodium ions reacting with nitrate ions Eg.: Calcium ions reacting with hydroxide ions Note: Use brackets for polyatomic ions if more than 1 is present in the molecule. Eg.: Ammonium ions reacting with dichromate ions

Practice KNO3 Ca(OH)2 Ag2SO4 NH4CN Pb(CO3)2 NOW YOU TRY IT! Hebden (p. 76) #95, 101, 103, 119, 125, 131, 135, 141,147, 156,158 Practice Give the Formula for: Potassium nitrate Calcium hydroxide Silver sulphate Ammonium cyanide Lead (IV) carbonate KNO3 Ca(OH)2 Ag2SO4 NH4CN Pb(CO3)2

International Union of Pure and Applied Chemistry 5. Names of Ionic Compounds using the IUPAC method (Nomenclature) The metallic or positive ion is always named first and their names DO NOT change Metals that can have more than one charge or valence need a Roman numeral in the name in order to indicate the charge on the ion. eg.: Iron (II) Fe2+ Lead (IV) Pb4+ Non-metal ions that are single elements change their endings to "ide“. eg.: Chlorine chloride Oxygen oxide Polyatomic ions do not change their names. ( You know one is there if there are more than 2 capital letters in the formula!) International Union of Pure and Applied Chemistry

PbCl2 PbCl4 Lead (II) chloride Lead (IV) chloride Try This…MULTI-VALENT METALS Eg.: Find the charge on the Pb ion in: PbCl2 PbCl4 Lead (II) chloride Lead (IV) chloride

Recall… Mono Di Tri Tetra Penta Hexa Hepta Octa Nona Deca 1 2 3 4 5 6 7 8 9 10 Mono Di Tri Tetra Penta Hexa Hepta Octa Nona Deca

6. Naming/Formulas for HYDRATES! Hydrates are molecules that include WATER in their structure. Eg. CuSO4·5H20 To name them… it’s easy… a) Name the Ionic/polyatomic compound first… b) Then use the proper prefix to indicate how many water (hydrate) molecules there are… So… If 5 waters = Pentahydrate If 3 waters = Trihydrate So… the full name of CuSO4·5H20 Copper (II) Sulphate Pentahydrate

What would you Name… Zn(CH3COO)2•2H2O Zinc Acetate Dihydrate What about the formula for … Calcium Nitrate Tetrahydrate Ca(NO3)2 • 4H2O

You try… Hebden Pg. 75 # 19,47,53, 59, 94,111,116,129,140,151,160

Practice Questions: Hebden (p. 75/76 evens 9 only do the ionic/Polyatomic ones – not covalent compounds!!