Summary of Nomenclature To correctly name a compound, you must first identify whether it is ionic, molecular or an acid. Ionic compounds are composed of metals and non-metals. Molecular compounds are composed of non-metals. Acids have one or more hydrogens bound to an anion. The hydrogens dissociate from the anion when placed in water. You should be able to provide the name if given the chemical formula AND be able to provide the chemical formula if given the name. Ionic Compounds An ionic compound is composed of a cation and an anion. Metals lose electrons to form cations. Non-metals gain electrons to form anions. Cations: There are three classes of cations, type 1, type 2, and polyatomic. Type 1 cations form only one cation (only 1 charge/oxidation state) Type 2 cations form more than one cation (more than 1 charge/oxidation state) Polyatomic cations are composed of more than 2 or more atoms bound together by a covalent bond. Type 1 cations include a) Group 1A elements – Li+, Na+, K+, Rb+, Cs+ b) Group 2A elements – Be2+, Mg2+, Ca2+, Sr2+, Ba2+ c) Some group 3A elements – Al3+, Ga3+, d) Some group 3B elements – Sc3+, Y3+, La3+ e) others – Zn2+, Cd2+, Ag+ To name a type 1 cation add the word ion after the element name. Ex. K+ potassium ion Sr2+ strontium ion Ga3+ gallium ion Type 2 cations include the rest of the elements, primarily the transition metals and metals in the lower periods of groups 3A through 6A. To name a type 2 cation, include the charge of the ion and add ion after the element name. Ex. Co2+ cobalt (II) ion Mo4+ molybdenum (IV) ion Mn+7 manganese (VII) ion Polyatomic cations include the ammonium ion (NH4+) and the mercury (I) ion Hg22+. In addition, there is the phosphonium ion (PH4+) and the hydronium (H3O+).Anions: There are two classes of anions, single atom (monoatomic) non-metals and polyatomic anions. Monoatomic anions are formed from group 4A through 7A elements. To name a monoatomic anion, add the suffix –ide to the root of the element and add the word ion. Group 7A F- fluoride ion Cl- chloride ion Br- bromide ion I- iodide ion Group 6A O2- oxide ion S2- sulfide ion Se2- selenide ion Te2- telluride ion Group 5A N3- nitride ion P3- phosphide ion As3- arsenide ion Polyatomic anions are of two general types, the oxoanions and the “others”. The ones you need to know are included in the table at the end of this handout. You need to know their formula, their charge, and their name. The general rules for polyatomic oxoanions: add the suffix ate to the stem of the name of the element other than oxygen, then add ion. if an element forms two oxoanions, differing by the number of oxygens in the anion, use –ate as the suffix for the anion with the most oxygens and –ite for the suffix for the anion with the fewer oxygens. Cl, Br, and I form a series of 4 oxoanions. Add the prefix per- to the oxoanion with the most oxygens and the prefix hypo- to the oxoanion with the least oxygens. if the oxoanion contains a hydrogen, add hydrogen to the beginning of the oxoanion name Ionic compounds: Ionic compounds are neutral so the total charge must add up to zero. (number of cations)(charge on cation) + (number of anions)(charge on anion) To name an ionic compound, name the cation first and the anion second. Do not include the word ion. Remember for a type II cation, the charge on the cation is part of the name. Molecular Compounds These compounds are composed of non-metals. The elements are held together by covalent bonds. You will be responsible for naming binary compounds, compounds composed of two elements. To name molecular compounds: name the elements in the order they appear add the suffix –ide to the stem name of the second element use prefixes to indicate the number of atoms do not add mono to the first element when two “o”s appear, you need write only 1 when an a in the prefix is followed by an o, you use only the oAcids Acids fall into two general categories, those containing oxygen and those that do not contain oxygen. To name acids that do not contain oxygen, add the prefix hydro- to the stem of the element name that is not hydrogen and add the suffix –ic. Finally, add the word acid. To name acids that contain oxygen, add the suffix –ic, if the anion ends in ate and add the suffix – ous, if the anion ends in ite. Finally, add the word acid. Some examples of mistakes to avoid: Br- is the bromide ion; BrO3- is the bromate ion P3- is the phosphide ion; PO43- is the phosphate ion Learn the list of type I cations Note the use of parenthesis in the following example: ammonium carbonate (NH4)(CO3)2 Note the difference in the following acids: HBrO4 is perbromic acid HBr is hydrobromic acid HBrO2 is bromous acid Some practice problems: Chemical formula to name Name to chemical formula a) LiH2PO4 a) chromium (III) carbonate b) Co2(SO3)3 b) strontium nitride c) Zn(CN)2 c) cesium hypochlorite d) HCN d) barium arsenate e) ICl3 e) gallium nitride f) Hg2S f) sodium phosphide Answers: a) lithium dihydrogen phosphate a) Cr2(CO3)3 b) cobalt (III) sulfite b) Sr3N2 c) zinc cyanide c) CsClO d) hydrogen cyanide d) Ba3(AsO4)2 e) iodine trichloride e) GaN f) mercury (I) sulfide f) Na3PIon Category Ion Formula Ion Name Acid Formula Acid Name Group IV A CO32- carbonate ion H2CO3 carbonic acid SiO32- siliconate ion Group V A NO3- nitrate ion HNO3 nitric acid NO2- nitrite ion HNO2 nitrous acid PO43- phosphate ion H3PO4 phosphoric acid AsO43- arsenate ion AsO33- arsenite ion SbO43- antimonate ion Group VI A SO42- sulfate ion H2SO4 sulfuric acid SO32- sulfite ion H2SO3 sulfurous acid SeO42- selenate ion H2SeO4 selenic acid SeO32- selenite ion H2SeO3 selenous acid TeO42- tellurate ion TeO32- tellurite ion Group VII A ClO4- perchlorate ion HClO4 perchloric acid ClO3- chlorate ion HClO3 chloric acid ClO2- chlorite ion HClO2 chlorous acid ClO- hypochlorite ion HClO hypochlorous acid BrO4- perbromate ion HBrO4 perbromic acid BrO3- bromate ion HBrO3 bromic acid BrO2- bromite ion HBrO2 bromous acid BrO- hypobromite ion HBrO hypobromous acid IO4-
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