Binary Ionic Compounds: Naming & Formulas Binary Ionic Compounds Binary Ionic Compounds Ionic compounds consisting of only two parts Ionic compounds consisting of only two parts Bi = 2 Bi = 2 “Binary” = 2 parts “Binary” = 2 parts Part 1 Part 1 Monoatomic cation Monoatomic cation 1 atom 1 atom Positively charged Positively charged Metal  left side of periodic table Metal  left side of periodic table Part 2 Part 2 Monoatomic anion Monoatomic anion 1 atom 1 atom Negatively charged Negatively charged Non-metal  right side of the periodic table Non-metal  right side of the periodic table

Naming Binary Ionic Compounds Steps for naming binary ionic compounds: Steps for naming binary ionic compounds: 1: Metal cation is ALWAYS named first 1: Metal cation is ALWAYS named first Keeps its own name Keeps its own name Do not change the cation name Do not change the cation name 2: Non-metal anion is ALWAYS named second 2: Non-metal anion is ALWAYS named second The ending of the anion name changes to the suffix, “-ide” The ending of the anion name changes to the suffix, “-ide”

Naming Binary Ionic Compounds Examples: Examples: Sodium & chlorine Sodium & chlorine  Sodium chloride  Sodium chloride Aluminum & chlorine Aluminum & chlorine  Aluminum chloride  Aluminum chloride Aluminum & oxygen Aluminum & oxygen  Aluminum oxide  Aluminum oxide Sodium & sulfur Sodium & sulfur  Sodium sulfide  Sodium sulfide

Transition Metals Transition metals are found in the middle of the periodic table Transition metals are found in the middle of the periodic table They often have more than one ionic charge They often have more than one ionic charge Can form two (2) different cations Can form two (2) different cations Indicate the charge using roman numerals in brackets when naming Indicate the charge using roman numerals in brackets when naming Roman numerals: Roman numerals: 1 = (I), 2 = (II), 3 = (III), 4 = (IV) 1 = (I), 2 = (II), 3 = (III), 4 = (IV) i.e. Iron & Oxygen  Iron has two possible charges: Fe 2+ and Fe 3+ i.e. Iron & Oxygen  Iron has two possible charges: Fe 2+ and Fe 3+ iron (II) oxide means Fe 2+ iron (III) oxide means Fe 3+

Binary Ionic Formulas Formula: Formula: Representation of a chemical compound using symbols & numbers Representation of a chemical compound using symbols & numbers The formula of an ionic compound must be neutral The formula of an ionic compound must be neutral Therefore the “positives” must equal the “negatives” Therefore the “positives” must equal the “negatives”

Writing Binary Ionic Formulas Step 1. Use your periodic table to determine the symbols and the charges of the atoms involved Step 1. Use your periodic table to determine the symbols and the charges of the atoms involved Write the symbol out EXACTLY as it appears on the periodic table  remember, the letters are case sensitive! Write the symbol out EXACTLY as it appears on the periodic table  remember, the letters are case sensitive! Indicate the ionic charge as a superscript Indicate the ionic charge as a superscript i.e.: i.e.: Sodium & Chlorine  Na + & Cl - Sodium & Chlorine  Na + & Cl - Aluminum & oxygen  Al 3+ & O 2- Aluminum & oxygen  Al 3+ & O 2-

Writing Binary Ionic Formulas Step 2. Make sure that the “positives” equal the “negatives”. Step 2. Make sure that the “positives” equal the “negatives”. Do this by crossing or switching the charges and placing them as subscripts Do this by crossing or switching the charges and placing them as subscripts Subscripts then indicate the NUMBER of atoms in the formula required to balance the charges  once the charges are crossed and become subscripts, they no longer have a charge Subscripts then indicate the NUMBER of atoms in the formula required to balance the charges  once the charges are crossed and become subscripts, they no longer have a charge i.e.: i.e.: Sodium & Chlorine  NaCl Sodium & Chlorine  NaCl Aluminum & oxygen  Al 2 O 3 Aluminum & oxygen  Al 2 O 3

Tricky Rules When an ion has a charge of (+1) or (- 1), there is no need to include it as a subscript When an ion has a charge of (+1) or (- 1), there is no need to include it as a subscript i.e.: Sodium & chlorine = NaCl, not Na 1 Cl 1 i.e.: Sodium & chlorine = NaCl, not Na 1 Cl 1 When a compound has two subscripts that are both even numbers, we want to reduce them to the lowest ratio possible When a compound has two subscripts that are both even numbers, we want to reduce them to the lowest ratio possible i.e.:Calcium & oxygen  Ca 2 O 2 reduces to  CaO i.e.:Calcium & oxygen  Ca 2 O 2 reduces to  CaO i.e.:Lead (IV) & oxygen  Pb 2 O 4 reduces to  PbO 2 i.e.:Lead (IV) & oxygen  Pb 2 O 4 reduces to  PbO 2

Writing Formulas with Transition Metals Remember, transition metals have more than one charge Remember, transition metals have more than one charge How can we determine the charge from a formula alone? How can we determine the charge from a formula alone? Answer: use the charge of the anion as a guide! Answer: use the charge of the anion as a guide! The charge of the anion will always be the same, so determine the charge of the anion and work backwards The charge of the anion will always be the same, so determine the charge of the anion and work backwards i.e.: i.e.: Fe 2 S 3 Fe 2 S 3  Charge on sulfur is ALWAYS 2-  Charge on sulfur is ALWAYS 2- Fe & S 2- Fe & S 2- Formula indicates that Fe has gotta be Fe 3+  iron (III) sulfide Formula indicates that Fe has gotta be Fe 3+  iron (III) sulfide FeS FeS  Charge on sulfur is ALWAYS 2-  Charge on sulfur is ALWAYS 2- Fe & S 2- Fe & S 2- Formula indicates that Fe has gotta be Fe 2+  iron (II) sulfide Formula indicates that Fe has gotta be Fe 2+  iron (II) sulfide

More Examples: calcium & iodine calcium & iodine AlF 3 AlF 3 Iron 3+ & oxygen Iron 3+ & oxygen CoF 2 CoF 2