Naming Compounds What's in a name? That which we call a rose By any other name would smell as sweet." - William Shakespeare, Romeo and Juliet (II, ii)

We can determine the formula of a compound by completing Lewis dot diagrams Valence is “the number of electrons an atom must gain, lose, or share to complete its octet” For representative elements valence starts at +1 (IA), climbs to 4 (IVA) and falls back to -1 (VIIA) E.g. what compound would form from C + S? Step 1 - write valences: C +4 S -2 Step 2 - cross down valences: C 2 S 4 Background: valences and formulas Step 3 - simplify formula: CS 2 a) Al,Br b) K,S c) Zn,O d) Mg,N e) C,Cl f) Cu,O AlBr 3 K2SK2SZnOMg 3 N 2 CCl 4 CuO or Cu 2 O

Ionic compounds (metal with 1 valence) Rules for naming Names end in -ide. Example: sodium chloride Metal (positive ion) comes 1st (not chorine sodide) Use the group valence for nonmetals Do not capitalize unless starting a sentence Give formula & name: Ca + I, O + Mg, Na + S = Ca +2 I -1 = CaI 2 = calcium iodide = Mg +2 O -2 = MgO = magnesium oxide = Na +1 S -2 = Na 2 S = sodium sulfide

Multiple Oxidation Numbers(valences) Transition Metals (middle of Periodic Table) can have more than one oxidation number or charge. This is why no oxidation #’s were assigned to these groups. Exceptions to this rule: Silver and Zinc. Silver is always a +1 and Zinc is always a +2. These 2 elements Do NOT have variable (changing ) oxidation #’s.

Name ends in -ide, positive/metal comes first The charge of the metal is indicated in parenthesis using roman numerals E.g. Cu +1 is copper(I), Cu +2 is copper(II) Numbers refer to valences not to #s of atoms Try: Cu +2 +Cl, Zn 2 + Cl, Co +2 +Cl, Hg+S (do both) Cu 2 +Cl = Cu 2 Cl 1 = CuCl 2 = copper(II) chloride Zn 2 +Cl = Zn 2 Cl 1 = ZnCl 2 = zinc chloride Co 2 +Cl = Co 2 Cl 1 = CoCl 2 = cobalt(II) chloride Hg+S = Hg 1 S 2 = Hg 2 S = mercury(I) sulfide Hg+S = Hg 2 S 2 = HgS = mercury(II) sulfide Multiple valence: IUPAC naming

Groups of atoms can also have valences “Polyatomic ions” are groups of atoms that interact as a single unit. E. g Ba 3 (PO 4 ) 2 = Compounds containing polyatomic ions So far we have given valences to single atoms Li + O Li +1 O -2  Li 2 O barium phosphate Naming compounds with polyatomic ions is similar to naming other ionic compounds You should note that compounds with polyatomic ions have names ending in -ate or -ite not -ide Note that most are negative, except ammonium Name: Ca(OH) 2, BaSO 4, NH 4 NO 3, Al 2 (CO 3 ) 3

- calcium hydroxide - Barium sulfate - ammonium nitrate - Aluminum carbonate Ca(OH) 2 BaSO 4 NH 4 NO 3 Al 2 (CO 3 ) 3 Compounds containing polyatomic ions

Covalent Compounds Covalent compounds differ from ionic compounds in two main ways. 1. Covalent compounds form by SHARING ELECTRONS -not transferring electrons. 2. Covalent compounds Do NOT contain metals. Covalent compounds only contain NONMETALS.

Naming covalent compounds -ide ending, each element has “prefix” 1mono 2di 3tri 4tetra 5penta 6hexa 7hepta 8octa 9nona 10deca prefix refers to # of atoms - not valence N 2 O 4 = dinitrogen tetroxide Exception: drop mono for first element CO 2 = carbon dioxide The first vowel is often dropped to avoid the combination of “ao” or “oo”. CO = carbon monoxide (monooxide) SO 2 = sulfur dioxide (doxide) Name: CCl 4, P 2 O 3, IF 7 P 4 O 10 = tetraphosphorus decoxide

Write and name the following covalent compounds (IUPAC) carbon tetrachloride diphosporus trioxide iodine heptafluoride CCl 4 P 2 O 3 IF 7 For more lessons, visit

Writing formulas for covalent compounds practice Write the formulas for the following covalent compounds: A.) C 4 P 3 B.) S 5 F 2 C.) PCl 6 D.) C 3 Br

Formulas Answers: A.) C 4 P 3 =tetracarbon triphosphide B.) S 5 F 2 = pentasulfur difluoride C.) PCl 6 = phosphorus hexachloride  D.) C 3 Br = tricarbon monobromide