Nomenclature ( Compounds: Formulas & Names) Dr. Ron Rusay Spring 2008 © Copyright 2008 R.J. Rusay

Chemical Formulas and Naming Molecular Formula: Elements’ Symbols = atoms Subscripts = relative numbers of atoms How are compounds named? CaCl 2 CCl 4 NaOH (NH 4 ) 2 CO 3 C 20 H 26 N 2 O (Ibogaine)

Nomenclature Nomenclature: the naming of compounds Governed by the IUPAC: International Union of Pure and Applied Chemistry International rules are updated periodically General schemes and examples follow:

Naming Compounds Name cation first, then anion Monatomic cation = name of the element Ca 2+ = calcium ion Anion = root + -ide Cl  = chlorine Binary Ionic Compounds: For example; CaCl 2 ide CaCl 2 = calcium chloride

Common Monatomic Cations and Anions

Common Cations and Anions

Naming Compounds (continued) metal forms more than one cation: Pb 2+ or possibly Pb 4+ ? Ambiguous? option 1) use Roman numeral in name If Pb 2+ is the cation; eg. PbCl 2 : PbCl 2 = lead (II) chloride or 2) use name (latinized) + suffix: -ous (lower) or -ic (higher) Binary Ionic Compounds (Type II): PlumbumPlumbous

Common Type II Cations

Naming Compounds (continued) Compounds formed between two nonmetals First element in the formula is named first. It is the more electropositive. Second element is named as if it were an anion. Use prefixes to count the # of atoms. Do not normally use mono as a prefix.- P 2 O 5 = diphosphorus pentoxide Binary compounds (Type III):

Prefixes & The Number of Atoms

Compounds with more than two different elements Polyatomic ions: [oxygen as the third atom]

QUESTION

ANSWER. 4)lithium chloride Section 2.8 Naming Simple Compounds (p. 57) Lithium is a Group IA metal, so it always forms a +1 ion. Therefore, no roman numeral is necessary.

QUESTION

ANSWER. 2)iron (II) oxide Section 2.8 Naming Simple Compounds (p. 57) Iron is a transition metal that forms more than one type of ion. A roman numeral is needed to indicate which ion is present in the compound.

QUESTION Of the following, which provides the most acceptable name for Fe 2 (C 2 O 4 ) 3 ? 1.Iron (II) oxalate 2.Iron (II) oxalate (III) 3.Iron (III) trioxalate 4.Iron (III) oxalate

ANSWER Choice 4 is correct. Since iron can form compounds where it is commonly a +2 or +3, the roman numeral must be provided to indicate the charge (+3 in this case.) Since the iron charge is specified it is not necessary to indicate the number of oxalate ions present. Section 2.8: Naming Simple Compounds

QUESTION Which of the following provides the correct name for Ca(H 2 PO 4 ) 2 ? 1.Calcium dihydrogen phosphate 2.Calcium (II) hydrogen phosphate 3.Calcium di-dihydrogen phosphate 4.Calcium (II) dihydrogen phosphate

ANSWER Choice 1 provides the correct name for Ca(H 2 PO 4 ) 2. It is not necessary to use roman numerals when an atom typically only has one oxidation state (such as calcium’s +2.) Also, the anion combination only has one possibility here so it does not need a prefix Ca(H 2 PO 4 ) 2. Section 2.8: Naming Simple Compounds

Naming Acids [Compounds with electropositive Hydrogen atom(s)]

QUESTION Hypochlorous acid is related to the anion found in common household bleach. Which of the following is that common anion? 1.ClO 4 – 2.ClO 3 – 3.ClO 2 – 4.ClO –

ANSWER Choice 4 represents the hypochlorite ion, ClO –, that can be made to form hypochlorous acid HClO. Section 2.8: Naming Simple Compounds

Names from Formulas Name the following SO 2 CaBr 2 Zn(NO 3 ) 2 PCl 5 ( NH 4 ) 2 SO 4 FeO HI (aq) HBrO NaClO 4

Names from Formulas Solutions: Sulfur dioxideCalcium bromide Zinc nitrate Phosphorus pentachlorideAmmonium sulfate Iron(II) oxide Hydroiodic acidHypobromous acid Sodium perchlorate

Formulas from Names Provide formulas for the following Sulfur trioxide Magnesium chloride Lead (IV) sulfate Diphosphorus pentasulfide Ammonium phosphate Iron (III) oxide Hydrobromic acid Chloric acid Sodium chlorite

Formulas from Names Solutions: SO 3 MgCl 2 Pb(SO 4 ) 2 P 2 S 5 ( NH 4 ) 3 PO 4 Fe 2 O 3 HBr HClO 3 NaClO 2