Naming and Writing Formulas for Compounds

Ionic Compounds Two Systems for naming: 1.Stock (Roman numerals) 2.Old System

Stock System Binary Compounds 1.Write the name of the positive ion 1 st 2.Check to see if it has more than one oxidation #. If it does determine the charge and use a Roman numeral to designate the charge 3.Write the root name of the negative ion. Change the ending to an – ide ending. Compounds with Polyatomic ions 1.Same steps as binary for positive ion 2.For negative ion, just write the name of the polyatomic *** DO NOT ADD THE ENDING –IDE

Determining Charge for Ions with Variable Oxidation #’s --Ions w/ more than one oxidation # (transition metals, groups 3-12) 1.Hg 2.Cu 3.Pb 4.Sn 5.Cr 6.Fe ***Note: Zn is +2 Ag is +1 Assign an oxidation # to the negative ion Ex. Hg Cl -1 Multiply the oxidation # by the subscript Ex. Hg Cl -1 1 Since the compound is neutral the overall charge must = 0 Ex. Hg+ 1 Cl -1 = = 0

Remember…. Roman numerals are only used for those ions with more than one charge!!!!!!!! 1.Sodium Chloride 2.Strontium chloride 3.Sodium hydroxide 4.Copper (II) chloride 5.Lead (IV) oxide 6.Copper (I) hydroxide 7.Mercury (II) bromide 8.Aluminum oxide 9.Strontium oxide 10.Mercury (II) oxide 1.NaCl 2.SrCl 2 3.NaOH 4.CuCl 2 5.PbO 2 6.CuOH 7.HgBr 2 8.Al 2 O 3 9.SrO 10.HgO

Old System 1. Write the name of the positive ion 1 st. Check to see if the ion has more than one oxidation #. If it does, determine the charge and add one of the following endings a)–ous for lower b)-ic for higher Remember… -ous is less -ic is more 2.Write the root of the negative ion 3.Add –ide if it is an element 4.Write the name of the ion if it is a polyatomic

Old System Names Cu +1 cuprous Hg +1 mercurous Fe +2 ferrous Pb +2 plumbous Sn +2 stannous Cu +2 cupric Hg +2 mercuric Fe +3 ferric Pb +4 plumbic Sn +4 stannic

1.Hg(OH) 2 2.SnCl 2 3.PbO 4.CuCl 5.FeO 6.Fe 2 O 3 7. HgOH 1.Mercuric hydroxide 2.Stannous chloride 3.Plumbous oxide 4.Cuprous chloride 5.Ferrous oxide 6.Ferric oxide 7. Mercurous hydroxide

1.Write the symbols for the ions side by side, with the positive ion 1 st 2.Cross over charges diagonally to give subscripts (Subscripts tell how many of each element are in the compound). 3.Check the subscripts to make sure the compound is neutral. 4.Do not write subscripts that are 1 (they are understood) 5.Do not write subscripts that are the same # 6.If the subscripts are divisible by the same #, reduce them to give the simplest ratio 7.If the compound contains a polyatomic ion that will have a subscript from crossing over, you must PUT PARENTHESIS AROUND IT!!!!

Examples Write the formula for: Strontium Chloride 1.Sr +2 Cl -1 2.SrCl 2 **subscripts that are 1 are not written Write the formula for: Magnesium Oxide 1.Mg +2 O -2 2.MgO ** subscripts that are the same # are not written

More Examples Write the formula for: Lead (IV) oxide ** remember, the Roman numeral tells you the oxidation # Pb +4 O -2 Pb 2 O 4 (these can be reduced) PbO 2 Write the formula for: Stannic sulfate Sn +4 SO 4 -2 (the –ic ending tells you that it is tin’s higher charge) Sn(SO 4 ) 2 ** the subscripts can be reduced and sulfate must have parenthesis because it is a polyatomic ion and it has a subscript that will be written

Write the formulas for: Lithium bromide Strontium sulfide Aluminum oxide Mercury (II) hydroxide Plumbic carbonate Ferrous oxide Ferric oxide Ammonium sulfate LiBr SrS Al 2 O 3 Hg(OH) 2 Pb (CO 3 ) 2 FeO Fe 2 O 3 (NH 4 ) 2 (SO 4 )

ONLY USED FOR NAMING COVALENTLY BONDED COMPOUNDS (Remember… this will be two nonmetals bonded together) Write the name of the least electronegative element 1 st. A prefix is used w/the name of the 1 st element only if more than one atom is present The second element always get a prefix Then write the root and add -ide

Numerical Prefixes for Binary Molecular NumberPrefix 1Mono 2Di 3Tri 4Tetra 5Penta 6Hexa 7Hepta 8Octa 9Nona 10Deca

Examples Name: 1.N 2 O Dinitrogen monoxide 2.NO Nitrogen monoxide 3.N 2 O 3 Dinitrogen trioxide

Writing Formulas for Binary Molecular Use the prefixes to tell you how many of each element is in the compound. Examples: 1.Disulfur trioxide S2O3S2O3 2.Carbon monoxide CO 3.Carbon tetrachloride CCl 4

Recognizing Acids At this very beginning level, you will recognize an acid by the fact that its formula starts with H, as in these examples: HCl HNO 3 H 2 SO 4 HClO 3 H 3 BO 3

The name of an acid is derived from its anion: For acids in which the anion is an element, the name of the acid begins with the prefix hydro- - The acid’s name also includes the root name of the anion and the word acid In addition, you must change the suffix of the anion to –ic Ex: HCl –Hydrochloric Acid For acids in which the anion is a polyatomic, the prefix hydro- IS NOT USED!!! Write the name of the polyatomic and: -Change –ate to –ic (or to – oric/-uric for a few cases) -And -ite to -ous Then write the word acid.

Name the following acids: 1) H 3 PO 4 2) H 2 CO 3 3) H 2 SO 4 4) HIO 3 5) HF 6) HNO 2 1)Phosphoric Acid 2)Carbonic Acid 3)Sulfuric Acid 4)Iodic Acid 5)Hydrofluoric Acid 6)Nitrous Acid

***Remember… the prefix “hydro-” means its an element bonded with hydrogen ***if “hydro-” is not present, then a polyatomic is bonded with hydrogen Write the formula for these acids: hydrobromic acid nitric acid sulfurous acid phosphorous acid acetic acid 1.HBr 2.HNO 3 3.H 2 SO 4 4.H 3 PO 3 5.HC 2 H 3 O 2