Inorganic Nomenclature

Transcription

1 Inorganic Nomenclature In order to efficiently be able to discuss chemicals and reactions, we need to understand a common system of chemical nomenclature. Nomenclature is crucial as you further your studies in chemistry understanding and utilizing proper terminology will help you in the lecture setting, and more importantly, in the lab. The IUPAC (International Union of Pure and Applied Chemists) system of nomenclature provides a set of rules for the naming compounds and writing formula. We are going to learn this system for inorganic compounds. Note: As we work through nomenclature, it is important that you know the names of elements and ions! Identifying the Type of Compound Before naming the compound, we must first classify the compound as an ionic compound or a molecular compound. Ionic compounds: Contains one or more metal ions. Exceptions: A molecule is also ionic if it contains hydrogen ions (H + ) or ammonium ions (NH 4 +). Molecular compounds: Contains nonmetals only. Once we have identified the type of compound, we can apply the appropriate rules of writing formula and naming compounds. We ll start with ionic compounds. Ionic Compounds: Writing formulas For all ionic compounds, the cation is listed before the anion. Step 1: Determine the charges for each ion. Step 2: Determine the how many of each ion is needed for charge neutrality. Check: Is the sum of the positive charges = the sum of negative charges? Step 3: Reduce the subscripts to give the smallest ratio of whole numbers. NaF, MgI 2, K 2S, HCl, What about polyatomic ions? Consider polyatomic ions as a package deal. The package must remain intact, and the charge applies to the entire package. When you need multiple polyatomic ions to equalize charge, put the entire package in parentheses, and then indicate the number of ions needed outside the parentheses. Ca(NO 3) 2, Li 2SO 4, (NH 4) 2O, Mg 3(PO 4) 2 Ionic Compounds: Naming compounds For all ionic compounds, the name consists of the cation name followed by the anion name. Type I Ionic Compounds These compounds are formed from cations that form only one ion, such as group I, II, and II metal ions. Some additions to this group are compounds that contain hydrogen ions, ammonium ions, and the transition metal ions silver (Ag + ), and zinc (Zn +2 ). Cation: takes the name of the element. Anion: the name of the polyatomic ion, or take the base name of the nonmetal, add -ide Example: nitrogen nitride chlorine chloride oxygen oxide Inorganic Nomenclature NF Su07 Page 1 of 5

2 Type II Ionic Compounds These compounds are formed from cations that form multiple ions. These cations are typically formed from transition metals and p-block metals. The naming method is similar, with the addition of the charge of the cation listed after the element name, in parentheses and in roman numerals. Ion IUPAC Name Cu +1 Cu +2 Copper (I) Copper (II) Hg 2 +2 Mercury (I) This is polyatomic! Hg +2 Sn +2 Sn +4 Cr +3 Mercury (II) Tin (II) Tin (IV) Chromium (III) Some examples of Type I and Type II compounds: Ca(NO 3) 2 Calcium nitrate BaCl 2 Barium chloride Sn(CO 3) 2 Tin (IV) carbonate FePO 4 Iron (III) phosphate Ammonium sulfide (NH 4) 2S Lead (II) chloride PbCl 2 Rubidium perchlorate Rb(ClO 4) 2 Iron (III) oxide Fe 2O 3 Molecular Compounds: Naming Binary Compounds In this course, we will only name binary compounds, or compounds that have two, and only two, types of nonmetal atoms combined together. Recall that these do not include hydrogen-containing compounds. Similar to the ionic compounds, the first element retains the name of the element, whereas the second takes the base and adds ide. For these compounds, the number of atoms of each element present is indicated using a greek prefix before the element name (or base), as shown below. The exception is that the prefix mono is not used for the first element. Greek prefix: mono- di- tri- tetra- penta- hexa- hepta- octa- nona- deca- Number: Diphosphorus pentoxide P 2O 5 Sulfur trichloride SCl 3 Carbon monoxide CO Arsenic pentafluoride AsF 5 Inorganic Nomenclature NF Su07 Page 2 of 5

3 Naming Acids some special rules Acids are compounds that form when hydrogen-ion compounds are dissolved in water (signified by an (aq) following the formula). They fall into two categories for naming: binary acids that contain H + and only one other element, and oxo acids that contain H + and a polyatomic anion that contains oxygen. Binary Acids To name a binary acid, replace the ide ending for the anion and replace it with ic, and add the prefix hydro-; acid is added as a separate word at the end. HBr Hydrogen bromide HBr (aq) hydrobromic acid H 2S Hydrogen sulfide H 2S (aq) hydrosulfuric acid (this is a deviation) If the compound is binary (hydrogen and a non-metal), the ide portion from the anion name changes to ic and a hydro precedes the root name for that non-metal element. In all acids, the word acid is part of the name notice the aq after the formula. Examples formula HX (g) HX (aq) HBr (g) HBr (aq) H 2S (g) H 2S (aq) name Hydrogen rootide (named like covalent compound) Hydrorootic acid hydrogen bromide (named like covalent cmpd) hydrobromic acid hydrogen sulfide (named like covalent cmpd) hydrosulfuric acid Oxo acids To name an oxo acid, drop the hydrogen from the compound name, change the ate anion ending to ic, and add acid as a separate work at the end. HClO 4 Hydrogen perchlorate HClO 4 (aq) perchloric acid HNO 3 Hydrogen nitrate HNO 3 (aq) nitric acid If the compound is ternary (hydrogen and a polyatomic ion): and the name ends in ate for the anion: if the species is a gas, it is named hydrogen polyatomic ion. If the species is aqueous, the ate from the polyatomic ion changes to ic, the hydro is dropped from the name and the word acid is added as a suffix. Inorganic Nomenclature NF Su07 Page 3 of 5

4 More examples: Examples formula H 2SO 4 (g) H 2SO 4 (aq) name hydrogen sulfate sulfuric acid HClO 4 (aq) anion is perchlorate perchloric acid HClO 3 (aq) anion is chlorate chloric acid HClO 2 (aq) anion is chlorite chlorous acid HClO (aq) anion is hypochlorite hypochlorous acid HCl (aq) anion is chloride hydrochloric acid Some polyatomic ions that we will learn throughout the term! Formula Name Formula Name NO - 3 nitrate ClO - 4 perchlorate NO - 2 nitrite ClO - 3 chlorate CrO 2-4 chromate ClO - 2 chlorite Cr 2O 2-7 dichromate ClO - hypochlorite CN - cyanide IO - 4 periodate SCN - thiocyanate IO - 3 iodate MnO - 4 permanganate IO - 2 iodite OH - hydroxide IO - hypoiodite O 2-2 peroxide BrO - 4 perbromate NH - 2 amide BrO - 3 bromate SO 2-4 sulfate BrO - 2 bromite SO 2-3 sulfite BrO - hypobromite PO 3-3 phosphite CO 2-3 carbonate PO 3-4 phosphate HCO - 3 hydrogen carbonate or bicarbonate HPO 2-4 hydrogen phosphate HSO - 4 hydrogen sulfate or bisulfate H 2PO - 4 dihydrogen phosphate HSO - 3 hydrogen sulfite or bisulfite C 2H 3O - 2 acetate HS - hydrogen sulfide CH 3COO - acetate NH + 4 ammonium Inorganic Nomenclature NF Su07 Page 4 of 5

5 TABLE 1 COMMON CATIONS AND THEIR OXIDATION NUMBERS 1+ Group IA (1A) 2+ Group IIA (2A) 3+ Group IIIA (3A) 4+ NH 4 + ammonium Cd 2+ cadmium Cu + copper (I) Cu 2+ copper (II) Cr 3+ chromium (III) Co 2+ cobalt (II) Co 3+ cobalt (III) Fe 2+ iron (II) Fe 3+ iron (III) Ni 2+ nickel (II) Ni 3+ nickel (III) Pb 2+ lead (II) Pb 4+ lead (IV) Pd 2+ palladium (II) Pd 4+ palladium (IV) Ag + silver Pt 2+ platinum (II) Pt 4+ platinum (IV) Sn 2+ tin (II) Sn 4+ tin (IV) Zn 2+ zinc Inorganic Nomenclature NF Su07 Page 5 of 5