CHEMICAL NOMENCLATURE Unit 05

Key Vocabulary IUPAC - International Union of Pure and Applied Chemistry  Responsible for chemical naming worldwide  Rules for naming and writing compounds Law of Definite Proportions – states that in samples of any chemical compound, the masses of the elements are always in the same proportions. Chemical Formula - Symbols for its constituent elements are used; also shows number of atoms present in smallest representative unit of the substance.

Key Vocabulary Oxidation Number – A measure of the charge of an atom if the electrons shared in bonding were held only by the more electronegative atom. For example, in water (H 2 O), oxygen is more electronegative than hydrogen. This would give oxygen all the electrons and an oxidation number of -2 and each hydrogen an oxidation number of +1. For simple atoms or ions, the oxidation number is equal to the ionic charge. For a neutral element like Helium (He), the oxidation number is 0.

Key Vocabulary Acid – compound that produces hydrogen ions (H + ) in solution. Base – compound that produces hydroxide ions (OH - ) in solution. Monatomic ion – a single atom with a + or – charge as a result of losing or gaining valence electrons.  Examples: Na + Al 3+ P 3- Br 1- Polyatomic ion – a tightly bound group of atoms that behaves as a unit and carries a charge.  Examples: NH 4 + NO 3 - OH - SO 4 2-

Transition Metals Many of the cations of transition metals have more than one common ionic charge.  Examples - cations of Iron: Fe 2+ and Fe 3+ This is also true for tin (Sn) and lead(Pb), the two metals in group 4A. Use the stock system to name these Stock system – as part of the name of the element, a Roman numeral in parentheses indicates the value of the charge.  Example: Fe 2+ = Iron (II) and Fe 3+ = Iron (III)  See page 144 in textbook, table 6.3 for more examples

Naming Simple Ionic Compounds Ionic Compound = cation + anion  1. write the name of the cation (metal) If transition metal, useRoman numeral in parentheses Example: Iron(II)  2. write the anion(nonmetal)—change ending to –ide Ex. NaClcation = Sodium anion = Chlorine Name = Sodium chloride

Practice CaI 2 Calcium iodide LiFLithium fluoride MgOMagnesium oxide BeF 2 Beryllium fluoride FeCl 2 Iron (II) chloride

Naming Ionic Compounds with Polyatomics Polyatomic ion review  1. write the name of the cation (metal) If transition metal, may need Roman numeral in parentheses  2. write the polyatomic ion— see common ones on your STAAR reference materials.  Special note: NH 4 + is the only positive polyatomic ion  See pp in textbook, table 6.4

Practice Na 2 SO 4 Sodium sulfate CaCO 3 Calcium carbonate Li 3 PO 3 Lithium phosphite NH 4 Cl Ammonium chloride

Writing Ionic Formulas Criss Cross Method  1. write chemical symbol for each element or polyatomic  2. find the charge for each element or polyatomic (Transition metal—look at the roman numeral)  3. criss cross the charges to the opposite subscript  Notes: if charges can be reduced, do so before crossing down Use parentheses for polyatomics

Practice Lithium fluorideLiF Calcium sulfideCaS Iron (III) chlorideFeCl 3 Potassium nitrideK 3 N

Practice with polyatomics Ammonium chlorideNH 4 Cl Sodium sulfateNa 2 SO 4 Magnesium carbonateMgCO 3

Naming Covalent Compounds Covalent compound review  No charges  Share electrons  2 or more nonmetals  Examples: CO 2, H 2 O, SF 2

You will be receiving a copy of this soon! Use prefixes to designate the subscript PrefixNumber Mono1 Di2 Tri3 Tetra4 Penta5 Hexa6 Hepta7 Octa8 Nona9 Deca10

CO 2  Carbon dioxide  Notes: the second element still takes the –ide ending Do not use mono for the first element

Practice S 2 O 4 Disulfur tetroxide FCl 3 Fluorine trichloride N 2 O Dinitrogen monoxide NO 2 Nitrogen dioxide

Writing covalent formulas Write the element symbol and add the prefix as subscript  DO NOT CRISS CROSS …PREFIX STAYS WITH ORIGINAL ELEMENT  Sulfur trioxide  Dinitrogen tetrafluoride  Hexasulfur pentaiodide