Nomenclature of Ionic Compounds Monatomic Ions Memorize the common monatomic ions formed by various metals and non metals given in the Periodic Table below Note that Non metal atoms gain electrons and form negatively charged anions excepting the noble gases Metal atoms lose electrons and form positively charged cations including all the metals not explicitly shown The charges of main group A metal and non metal ions tend to follow group trends Naming monatomic ions The names of monatomic non metal anions are based on the original element name but end in ide The names of monatomic metal cations are the same as the original element names However when metals form more than one cation their charge must be included in the name as Roman Numerals in brackets 1A 2A 3A 4A 5A 6A H 1 Li 1 Be 2 Na 1 Mg 2 C 4 Transition Metals B Ti 2 Ti 3 Ti 4 Cr 2 Cr 3 Cr 6 Mn 2 Mn 3 Mn 4 Al 3 P 3 S 2 Cl 1 As 3 Se 2 Br 1 Sr 2 Ag 1 Cd 2 In 1 In 3 Sn 2 Sn 4 Cs 1 Ba 2 Au 1 Au 3 Hg2 2 Hg 2 Tl 1 Tl 3 Pb 2 Pb 4 Fr 1 Ra 2 Ca Rb 1 Ni 2 Ni 3 F 1 Ga 3 K Co 2 Co 3 O 2 Zn 2 2 Fe 2 Fe 3 N 3 Cu 1 Cu 2 1 7A I 1 Bi 3 Bi 5 At 1 8A Polyatomic Ions Many ionic compounds also contain polyatomic ions Memorize the list of polyatomic ions given in the table below OH 1 CN 1 SCN 1 HCO3 1 HSO3 1 HSO4 1 C2H3O2 1 NO2 1 NO3 1 MnO4 1 ClO 1 ClO2 1 ClO3 1 ClO4 1 Hydroxide Cyanide Thiocyanate Bicarbonate Hydrogen Carbonate Bisulfite Hydrogen Sulfite Bisulfate Hydrogen Sulfate Acetate Nitrite Nitrate Permanganate Hypochlorite Chlorite Chlorate Perchlorate O2 2 CO3 2 SO3 2 SO4 2 S2O3 2 C2O4 2 CrO4 2 Cr2O7 2 Peroxide Carbonate Sulfite Sulfate Thiosulfate Oxalate Chromate Dichromate PO3 3 PO4 3 Phosphite Phosphate NH4 1 Hg2 2 Ammonium Mercury I Note that Most polyatomic ions are negatively charged anions Polyatomic anions containing oxygen are called oxyanions The names of most polyatomic anions end in ate or ite In a given homologous series the anion ending in ate has one more oxygen atom than the anion ending in ite Combining Ions to Obtain Ionic Compound Formulas and Names The names and formulas of ionic compounds always start with the positively charged cation metal or ammonium The oppositely charged ions are combined in simple whole number ratios to yield a net neutral ionic compound These ratios become the subscripts in the compound formula Ion charges are never shown in the compound formula The name of the compound is obtained by simply combining together the cation name with the anion name Prefixes are never used
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