Naming Compounds Handout IONIC COMPOUNDS versus MOLECULAR COMPOUNDS or MOLECULES ionic compound consist of cations positive ions and anions negative ions held together by electrostatic attraction usually a metal nonmetal s made of monatomic ions polyatomic ions and or both monatomic ions consist of a single atom polyatomic ions consist of more than one atom molecular compound or molecule consist of nonmetal atoms held together by covalent bonds acid a molecule that releases H ions in water NAMING MONATOMIC CATIONS Metal atoms lose valence electrons to form positively charged ions called cations An ion formed from an individual atom is a monatomic or monoatomic cation I Groups IA to IIA elements aluminum Al silver Ag zinc Zn and cadmium Cd form only one type of ion each Group IA elements form 1 ions Li Na K Rb Cs 2 2 2 2 2 Group IIA elements form 2 ions Be Mg Ca Sr Ba 3 2 2 aluminum ion Al silver ion Ag zinc ion Zn cadmium ion Cd These ions are named as follows e g Na sodium ion element name ion 2 Sr 2 strontium ion Zn zinc ion II The Stock system is used to name transition metals Sn and Pb that each form more than one ion element name charge in Roman numerals ion e g 2 Fe 3 Fe 2 iron II ion Pb iron III ion Pb SCCC MV Naming Compounds Handout v0411 lead II ion 4 lead IV ion Cu copper I ion 2 Cu copper II ion page 1 of 11 Name each of the following monatomic cations Li Cd 2 Ag Cu 2 Al 3 Mg 2 Ni 3 Sn 4 H Co 3 Fe 3 Na K Hg 2 Ca 2 Zn 2 NAMING MONATOMIC ANIONS Nonmetal atoms gain valence electrons to form negatively charged ions called anions When a nonmetal forms an ion it is named element stem name ide ion e g O oxygen atom N nitrogen atom O P phosphorus atom 2 oxide ion 3 N nitride ion 3 P phoshide ion Name each of the following monatomic anions F Br I SCCC MV Naming Compounds Handout v0411 Cl 2 S 3 P page 2 of 11 NAMING POLYATOMIC IONS Ions made up of more than one atom are polyatomic ions only one polyatomic cation NH4 ammonium ion many polyatomic anions see table below Common Polyatomic Ions NH4 ammonium ion Hg22 mercury I ion CrO42 chromate ion Cr2O72 dichromate ion SO42 sulfate ion SO32 sulfite ion NO3 nitrate ion NO2 nitrite ion OH hydroxide ion O22 peroxide ion MnO4 permanganate ion C2H3O2 acetate ion PO43 phosphate ion CN cyanide ion SCN thiocyanate ion CO32 carbonate ion HCO3 bicarbonate or hydrogen carbonate ion ClO hypochlorite ion ClO2 chlorite ion ClO3 chlorate ion ClO4 perchlorate ion WRITING CHEMICAL FORMULAS GIVEN INDIVIDUAL IONS Compounds must be neutral total ve charge total ve charge 1 If the two ions have exactly opposite charges 1 and 1 2 and 2 3 and 3 formula of the compound contains one of each ion e g Na 2 Ca 3 Al Cl 2 S 3 N NaCl CaS AlN K NO3 2 Ba 3 Fe KNO3 2 BaSO4 3 SO4 PO4 FePO4 Combine each pair of ions to get the formula of the compound they form NH4 Sr 2 Na 2 Ni F 2 CO3 C2H3O2 2 CrO4 Li Al CN 3 3 PO4 K OH SCCC MV Naming Compounds Handout v0411 Fe 3 3 N page 3 of 11 2a If two monatomic ions have different charges use the crossover method to get the formula of the compound The superscript for the cation becomes the subscript for the anion The superscript for the anion becomes the subscript for the cation Finally simplify subscripts to get the lowest ratio of ions Note Only the NUMBERS cross down not the signs e g Na S 2 Ba 2 N 3 Ti 4 O 2 Na2S Ba3N2 TiO2 Ti2O4 is simplified b If two ions have different charges and at least polyatomic ion is involved use crossover rule to get formula of the compound if more than one of polyatomic ion in formula use parentheses simplify subscripts to get lowest ratio of atoms Note Again only the numbers cross down not the signs e g NH4 SO4 2 Ca 2 NO3 Pb 4 CO3 2 NH4 2SO4 Ca NO3 2 Pb CO3 2 Pb2 CO3 4 is simplified Combine each pair of ions to get the formula of the compound they form Cu Li 2 O CO3 2 4 Sn 3 Fe SCCC MV Naming Compounds Handout v0411 Cl 2 S K 2 Ni 3 P PO4 3 page 4 of 11 CHEMICAL FORMULAS AND NAMES FROM INDIVIDUAL IONS Compounds are named from the individual ions they come from Name the cation and the anion then remove ion from each name e g Na Cl sodium ion chloride ion NaCl sodium chloride potassium ion 2 CO3 carbonate ion K 3 Fe NO3 Ag 2 S iron III ion nitrate ion silver ion sulfide ion K2CO3 potassium carbonate Fe NO3 3 iron III nitrate Ag2S silver sulfide Combine each pair of ions to get the chemical formula then name the compound Individual ions Mg 2 Ni 2 F S 2 Compound Formula Compound Name MgF2 magnesium fluoride Ca 2 Br Cu 2 P 3 Co 2 NO2 K CrO4 2 Al 3 O 2 SCCC MV Naming Compounds Handout v0411 page 5 of 11 GIVEN THE CHEMICAL FORMULA NAME THE COMPOUND WHEN THE METAL CATION FORMS ONLY ONE CHARGE 1 If the metal is in Groups IA IIA aluminum silver cadmium or zinc then just name the metal cation and the anion e g NaCl Na sodium and Cl chloride NaCl sodium chloride BaI2 Ba2 barium and I iodide BaI2 barium iodide Al OH 3 Al3 aluminum OH hydroxide Al OH 3 aluminum hydroxide ZnSO4 Zn2 zinc and SO4 2 sulfate ZnSO4 zinc sulfate WHEN THE METAL CATION FORMS MULTIPLE CHARGES 2 If the metal can form more than one ion a Use the charge on the anion to determine the overall negative charge b Since an ionic compound is neutral overall charge is zero the overall positive charge must equal the overall negative charge c If there is more than one of the cation present divide the overall positive charge by the number of cations present to get the charge for each cation d Name the cation and the anion then remove ion from both e g Ni Br2 Br has a 1 charge so 2 Br 2 2 overall positive charge 2 Ni 2 Ni nickel II ion Br bromide ion NiBr2 nickel II bromide If a polyatomic ion is involved remember that more than one polyatomic is shown in parentheses i e DO NOT confuse the subscripts of the ATOMS in a polyatomic ion with the number of polyatomic ions present e g Fe2 SO4 3 SCCC MV Naming Compounds Handout v0411 2 SO4 has a 2 charge so 3 SO4 6 overall positive charge 6 2 Fe 6 3 each Fe must be 3 Fe 3 2 Fe iron III ion SO4 sulfate …