UNIT 5: IONIC COMPOUNDS NOTES ***Refer to Ion Charge Chart and Periodic Table for Reference Review Compounds Simple Ions All atoms want to have a full outer set of valence electrons this makes them Octet Rule: have 8 valence electrons o Duet Rule: For smaller atoms (H, He, Li, Be) they only need 2 VE to be stable Most atoms don t have a full outer set of valence electrons so they form to become stable. Compounds form when elements, or electrons Ionic Compound: when one element and another element o Formed between a and a Covalent Compound: when two elements o Formed between Ion: Positive charge occurs when atom Negative charge occurs when atom Cation: o Usually o Anion: o Usually o Ionic Compounds + = Ionic compounds are (zero charge) o Which means o = (0) net charge =
Tricks and Tips/Charges 1 18 So group 1 elements have a charge of, group 2 elements have a charge of, group 13 elements have a charge of ; group 15 elements have a charge of ; group 16 elements have a charge of ; and group 17 elements have a charge of. Groups 3-12 and 14 have varying charges. Binary Compounds Writing their Names Binary compounds are Remember: Overall charge on compound is NEUTRAL (ZERO) Rules: 1. is written and named first a) Borrow names from b) 2 or more possible ions: Example: Copper can be either OR Look at the formula to determine which ion was used Common multiples: Cobalt, Copper, Iron, Lead, Nickel, Tin (USE CHARGE CHART) 2. is written second a) Borrow names from but change ending to -
Examples 1. BeS o Does the cation have multiple ions? o Beryllium s charge: o Beryllium has a charge; sulfur has a charge, so they, leaving o Name of Compound/Answer: 2. FeCl 3 o Does the cation have multiple ions? o Iron s charges: or ; chlorine s charge is o Look at the subscript on the ( ) to determine iron s charge o There s a on the Cl of the compound andcl has a charge, so the charge on iron must be (Reason: (1 x 3+) + (3 x 1-) = zero) o Since the cation has you must include a after its name to indicate its charge o Name of compounds/answer: Practice Problems: Write the names for the following ionic binary compounds: 1. NaCl: 2. KI: 3. CaF 2: 4. CuCl 2: 5. FeO: Binary Compounds Writing their Formulas Use CHARGES of elements to determine REMEMBER: Overall charge must still be ZERO/NEUTRAL, so total positive charge MUST EQUAL total negative charge Rules: 1. Write the symbol for the, including its a) If it s a multiple-charge ion, use its to determine charge 2. Write the symbol for the, including its 3. Use the elements symbols and swap their charges to go with the opposite element; the charges now become on the opposite element a) This allows the compound s charge to be NEUTRAL 4. If the charges are the same, they Examples 1. Magnesium Oxide: o Swap the charges likes cancel each other out o Mg 2+ O 2- o Answer: o Check for neutrality: Mg: O:
2. Potassium Oxide: o Swap the charges likes cancel each other out o K 1+ O 2- o Answer: o Check for neutrality: K: O: Practice Problems: Write the formulas for the following ionic binary compounds: 1. Lithium Sulfide: 2. Calcium Bromide: 3. Aluminum Bromide: 4. Lead (II) Sulfide: 5. Iron (III) Oxide: Polyatomic Ions Polyatomic Ions are Oxyanion: Follows same rules as ionic compounds, but don t change anion ending See Polyatomic Ion Chart Practice Problems: Write the names/formulas for the following ionic compounds: 1. Potassium Hydroxide: 2. Silver Sulfate: 3. Ammonium Chloride: 4. Beryllium Nitrate: 5. Potassium Chlorate: 6. BaSO 4: 7. Na 2CO 3: 8. HgBr 2: 9. Cu(NO 3) 2: 10. Mg 3(PO 4) 2: Covalent Compounds Form between two when they electrons Naming is easier use in front of element name If there is only one atom of the first element, that name gets no prefix Second element Ending of second element is
Prefix Chart: Examples: 1. CO 2 There is carbon, so it gets. There are oxygens, so the prefix for that will be 2. H 2O There are hydrogens, so its prefix will be. There is oxygens, so its prefix will be 3. Phosphorus trichloride No prefix on phosphorus so there will be phosphorus. Prefix on chloride is tri- so there will be chlorines Answer: 4. Dinitrogen trioxide Prefix on nitrogen is di-, so there will be nitrogens. Prefix on oxide is tri- so there will be oxygens Practice Problems: Write names/formulas of covalent compounds 1. CO: 2. SO 2: 3. CH 4: 4. N 2O 5: 5. Nitrogen monoxide: 6. Chlorine trifluoride: 7. Diphosphorus pentoxide: