Nomenclature (Compounds: Formulas & Names)

Dr. Ron Rusay

Spring 2008

© Copyright 2008 R.J. Rusay© Copyright 2008 R.J. Rusay

Chemical Formulas Chemical Formulas and Namingand Naming

Chemical Formulas Chemical Formulas and Namingand Naming

• Molecular Formula:

• Elements’ Symbols = atoms

• Subscripts = relative numbers of atoms

• How are compounds named?

CaCl2 CCl4 NaOH (NH4)2CO3

C20H26N2O (Ibogaine)

NomenclatureNomenclature

• 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 CompoundsNaming Compounds

• Name cation first, then anion

• Monatomic cation = name of the element

• Ca2+ = calcium ion

• Anion = root + -ide

• Cl = chlorine

Binary Ionic Binary Ionic Compounds:Compounds:For example; CaCl2

ide

CaCl2 = calcium chloride

Common Monatomic Cations and Anions

Common Cations and Anions

Naming Compounds(continued)

Naming Compounds(continued)

• metal forms more than one cation: Pb2+ or possibly Pb4+ ? Ambiguous?

• option 1) use Roman numeral in name

• If Pb2+ is the cation; eg. PbCl2 :

• PbCl2 = lead (II) chloride

• or 2) use name (latinized) + suffix: -ous (lower) or -ic (higher)

Binary Ionic Compounds (Type Binary Ionic Compounds (Type II):II):

Plumbum Plumbous

Common Type II Cations

Naming Compounds(continued)

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.-

• P2O5 = diphosphorus pentoxide

Binary compounds (Type III):Binary compounds (Type III):

Prefixes & The Number of Atoms

Compounds with more than two different elements

• Polyatomic ions: [oxygen as the third atom]http://chemconnections.llnl.gov/general/Chem120/polyatomics.html

QUESTIONThe correct name for LiCl is: 1) lithium monochloride. 2) lithium (I) chloride. 3) monolithium chloride. 4) lithium chloride. 5) monolithium monochloride.

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.

QUESTIONThe correct name for FeO is: 1) iron oxide. 2) iron (II) oxide. 3) iron (III) oxide. 4) iron monoxide. 5) iron (I) oxide.

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.

QUESTIONOf the following, which provides the most acceptable name for Fe2(C2O4)3?

1. Iron (II) oxalate2. Iron (II) oxalate (III)3. Iron (III) trioxalate4. Iron (III) oxalate

ANSWERChoice 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

QUESTIONWhich of the following provides the correct name for Ca(H2PO4)2?

1. Calcium dihydrogen phosphate2. Calcium (II) hydrogen phosphate3. Calcium di-dihydrogen phosphate4. Calcium (II) dihydrogen phosphate

ANSWERChoice 1 provides the correct name for Ca(H2PO4)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(H2PO4)2.

Section 2.8: Naming Simple Compounds

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

QUESTIONHypochlorous acid is related to the anion found in common household bleach. Which of the following is that common anion?

1. ClO4–

2. ClO3–

3. ClO2–

4. ClO–

ANSWERChoice 4 represents the hypochlorite ion, ClO–, that can be made to form hypochlorous acid HClO.

Section 2.8: Naming Simple Compounds

Names from FormulasName the following

• SO2 CaBr2 Zn(NO3)2

• PCl5 ( NH4)2SO4 FeO

• HI(aq) HBrO NaClO4

Names from Formulas

• Solutions:• Sulfur dioxide Calcium bromide Zinc nitrate

• Phosphorus pentachloride Ammonium sulfate Iron(II) oxide

• Hydroiodic acid Hypobromous acid Sodium perchlorate

Formulas from Names Provide formulas for the following

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 NamesFormulas from Names

• Solutions:

• SO3 MgCl2 Pb(SO4 )2

• P2S5 ( NH 4 )3PO4 Fe2 O3

• HBr HClO3 NaClO2