Naming Ionic Compounds

Naming Ionic Compounds I. Naming Ions A. Cations (+ions) 1. Element name followed by "ion" (when in Group IA, IIA, Al 3+, Ga 3+, Zn 2+, Cd 2+, Ag +, Ni 2+ ). Na + sodium ion, K + potassium ion, Al 3+ aluminum ion (NO Roman Numeral) 2. If an element has cations of different charges (ones not listed above), a. Element name (ion charge in Roman Numerals) +"ion" recognize only (b. Latinized element name with endings: -ous for the lower charged ion; -ic for higher charged ion) Fe2+ iron(ii) ion (or ferrous ion ) Fe3+ iron(iii) ion (or ferric ion ) Cu+ copper(i) ion (or cuprous ion ) Cu2+ copper(ii) ion (or cupric ion ) Sn2+ tin(ii) ion (or stannous ion ) Sn4+ tin(iv) ion (or stannic ion ) B. Anions (-ions) 1. Element name (w/o its ending) with suffix -ide +"ion" for anions of one element alone. H- hydride ion I- iodide ion O 2 - oxide ion S 2 - sulfide ion 2. Learn name and charge of polyatomic ions (covalently bonded group of atoms: stable and electrically charged) a. Know: OH- hydroxide ion, CN- cyanide ion, C2H3O2 - (or CH3COO-) acetate ion, (also one +ion NH4 + ammonium ion) b. learn others from acid names i) using -ate to show oxygen, when acid has -ic ending) ii) iii) ACID H 2 SO 4 sulfuric acid HNO 3 nitric acid H 3 PO 4 phosphoric acid OXYANION SO 4 sulfate ion NO 3 - nitrate ion PO 4 phosphate ion H 2 carbonic acid carbonate using -ite to show combination with fewer oxygen atoms. (Acid has -ous ending) H 2 sulfurous acid sulfite ion HNO 2 nitrous acid NO 2 - nitrite ion using hydrogen (or bi-) before oxyanion name to show hydrogen in ion HSO 4 - hydrogen sulfate (or bisulfate) ion H - hydrogen carbonate (or bicarbonate) ion HPO 4 hydrogen phosphate, H2 PO 4 - dihydrogen phosphate 1

Names of Some Important Oxyanions* (Learn the seven ions ending with ate & the others from them.) *No ions where not shown. Hypo ite ite ate Per ate (Two fewer (One Fewer (Learn the 7 below & (One More Oxygen Atoms) Oxygen Atom) rules to go to more/less O) Oxygen Atom) ClO- ClO 2 - ClO 3 - Chlorate ClO 4 - BrO- BrO 2 - BrO 3 - Bromate BrO 4 - IO- IO 2 - IO 3 - Iodate IO 4 - PO 2 PO 3 PO 4 Phosphate NO 2 - NO 3 - Nitrate SO 4 Sulfate Carbonate II. Naming compounds Cation name first, then anion name (w/o "ion" after names). Use charge on ion to find charge of +ion for Roman Numeral. NaCl sodium chloride, CaH 2 calcium hydride, FeCl 3 Iron(III) chloride, PbO 2 lead(iv) oxide, Na 2 sodium carbonate, NH 4 HSO 4 ammonium hydrogen sulfate III. Writing formulas from names. A. Cation symbol then anion symbol (without charge) using the smallest whole number subscripts to tell ratio of kinds of atoms to give an electrically neutral compound. Lithium iodide LiI, Magnesium chloride MgCl 2 B. Parentheses around polyatomic ions when subscripted. Aluminum hydroxide Al(OH) 3 Aluminum sulfate Al 2 (SO 4 ) 3 Ammonium carbonate (NH 4 ) 2 Potassium hydrogen phosphate K 2 HPO 4 Formulas must be electrically neutral (i.e. +charges of ions must balance - charges of ions). Naming Inorganic Covalent Molecules NUMERICAL PREFIX SYSTEM (use for 2 nonmetals, i.e. covalent molecules) 1. Write the name of the less EN element 2. Write more EN element (w/o its ending) + -ide 3. In front of each use a prefix to tell the # of atoms of that element. (Mono- is often dropped particularly in front of the first name. An o or a at the end of prefix is dropped with oxide: monoxide, hexoxide.) LEARN PREFIXES! (1 mono, 2 di, 3 tri, 4 tetra, 5 penta, 6 hexa, 7 hepta, 8 octa, 9 nona, 10 deca) Naming Acids of H with an anion without oxygen: use a hydro- prefix & -ic ending on root + acid. HCl (aq) hydrochloric acid; HCN (aq) hydrocyanic acid Naming acids containing O: -ate ion becomes -ic acid, etc. HC 2 H 3 O 2 acetic acid; HIO hypoiodous acid 2

NOMENCLATURE OF INORGANIC COMPOUNDS GENERAL: There are at present two methods of naming inorganic compounds: (1) The Roman Numeral System (also referred to as the Stock System). (2) The Numerical Prefix System. Actually, there are other older methods of naming compounds still in use but these two methods are now the official ways to name compounds. ROMAN NUMERAL SYSTEM: (Used for ionic compounds) General Rules: In the Roman Numeral System the following rules usually hold: element. (1) Write down the name of the less electronegative element or polyatomic ion. (2) Write down the proper designation for the other element or polyatomic ion. (3) Between the first and second words place a Roman Numeral in parentheses. The Roman Numeral is numerically equal to the oxidation state of the first Rules for Binary Compounds: Binary compounds are those compounds containing two different elements. (1) Write down the name of the less electronegative element. (2) Write down the first part of the name of the other element & add IDE (3) Between the two words place a Roman Numeral which is numerically equal to the oxidation state of the first element. Example: Cu 2 S The name of the first element is COPPER. The proper designation for the second element is SULFIDE. Since the oxidation state of copper in this compound is plus one, the Roman Numeral used is (I). Thus, the name for this compound is as follows: copper (I) sulfide. Example: CrCl 3 The name of the first element is CHROMIUM. The proper name for the second element is CHLORIDE. The oxidation state of chromium in this compound is plus three. So, the Roman Numeral to be used is (III). Thus, the compound is named chromium (III) chloride. Rules for Naming Compounds Containing More Than Two Elements: These compounds usually contain polyatomic ions. The following rules apply for those compounds that can be named using two words (also in those cases in which the polyatomic ion itself is named using two words). (1) Write down the name of the less electronegative element or polyatomic ion. (2) Write down the proper word for the other element or polyatomic ion. (3) Place a Roman Numeral after the positive element which is numerically equal to its oxidation state. 3

Example: HgSO 4 The name of the positive element is MERCURY. The name of the polyatomic ion is SULFATE. The oxidation state of mercury is plus two. Thus the Roman Numeral is (II). The compound is therefore named, mercury (II) sulfate. Example; Fe 2 (CrO 4 ) 3 The name of the positive element is IRON. The proper name for the polyatomic ion, CrO 4 is CHROMATE. The oxidation state of iron in this compound is plus three. Thus, the Roman Numeral is (III). The name of this compound, therefore, is iron (III) chromate. Additional Rules and Comments: There are some cases in which it is not necessary to indicate the Roman Numeral. Elements in Group IA and IIA and aluminum, gallium, zinc, cadmium, silver* and nickel* have only one oxidation state when they are present in compounds. Therefore, the oxidation state is understood and it is not proper to write the Roman Numeral, between the two words in the name of the compound. Examples: Ba(NO 3 ) 2 barium nitrate; K 2 O potassium oxide NUMERICAL PREFIX SYSTEM: (Used for covalent compounds, i.e. molecules) Recommended nomenclature for combinations of non-metals. (Stock System above is used for metal and non-metal binary compounds.) General Rules: In the Numerical Prefix System the following rules usually hold: (1) Write down the name of the less electronegative (2) Write down the proper designation for the name of the other element. Use -ide ending. (3) In front of each word write down the number of atoms of each element in the formula. This number is written in appropriate Latin or Greek notation. Example: P 2 O 5 The name of the first element is PHOSPHORUS. The proper designation for the second element is OXIDE. There are two atoms of phosphorus in the molecule; thus, DIPHOSPHORUS. There are five atoms of oxygen; thus. PENTOXIDE. Therefore, the compound is named diphosphorus pentoxide. Example: NO 2 nitrogen dioxide or mononitrogen dioxide. (Mono is frequently omitted from the designation for the first element named.) CO - carbon monoxide or monocarbon monoxide. *Has other oxidation states in a few less commonly observed compounds. 4

Proper Names of Second Elements in Binary Compounds: In order to name binary compounds the following words for the more negative element must be learned: S 2 - N 3 - sulfide H - hydride nitride OH - hydroxide P 3 - phosphide Se 2 - selenide F - fluoride O 2 - Cl - chloride O 2 Br - bromide O 2 oxide peroxide superoxide I - iodide CN - cyanide. Proper Names of Polyatomic ions: In order to name polyatomic ions in compounds the following words for the polyatomic ions must be learned: (BO 3 ClO 4 C1O 3 ClO 2 borate) C 2 O 4 perchlorate S 2 O 3 chlorate (AsO 4 chlorite C 2 H 3 O 2 oxalate thiosulfate arsenate) acetate ClO - hypochlorite SCN - thiocyanate SO 4 sulfate HSO 4 hydrogen sulfate sulfite H hydrogen sulfite NO 3 nitrate carbonate NO 2 nitrite H hydrogen carbonate CrO 4 chromate PO 4 phosphate Cr 2 O 7 dichromate HPO 4 hydrogen phosphate MnO 4 permanganate H 2 PO 4 dihydrogen phosphate NH 4 + (positive ions) 2+ ammonium Hg 2 mercury (I) 5

COMMON CHARGES OR OXIDATION STATES for metal ions (Bold use no Roman Numeral) Al +3 Ga +3 Fe +2, +3 Co +2, +3 Cu +1, +2 Ni +2 Hg +1, +2 Zn +2 Sn +2, +4 Ag +1 As +3, +5 Au +1, +3 Sb +3, +5 Mn +2, +3, +4 Bi +3, +5 Cd +2 Cr +2, +3 Pb +2, +4 CORRESPONDING ACID AND ANION NOMENCLATURE ACID EXAMPLE ANION EXAMPLE Per..ic HClO 4 Perchloric acid per..ate ClO 4 - Perchlorate...ic HClO 3 chloric acid...ate ClO 3 - chlorate...ous HClO 2 chlorous acid ite ClO 2 - chlorite hypo...ous HClO hypochlorous acid hypo ite ClO- hypochlorite hydro...ic HCl hydrochloric acid ide Cl- chloride LATIN AND GREEK NUMBER NOTATIONS mono 1, di 2, tri 3, tetra 4, penta 5, hexa 6, hepta 7, octa 8, nona 9, deca 10 WORK SHEET Name the following compounds by the more appropriate method. (Only one name per compound can be more appropriate.) Give molecular formulas for named compounds. COMPOUND STOCK SYSTEM NUMERICAL PRE SYSTEM SO 2 Al 2 O 3 Bi 2 (SO 4 ) 3 S 2 O 7 Carbon dioxide 6

Cr 2 S 7 IF 5 NO Phosphorus trichloride CaC 2 BP Sodium nitrate N 2 O 4 ZnBr 2 SiS 2 SnCl 4 Tetraphosphorus hexasulfide Sb 2 ( ) 5 PCl 3 FeO N 2 O 4 KClO 2 P 2 Se 3 Mg(CN) 2 ICl 3 Co(H ) 2 TeI 4 Ba(NO 2 ) 2 CdCr 2 O 7 CuMnO 4 Hg 2 Cl 2 VF 5 PbCrO 4 Manganese (IV) oxide Strontium iodide 7