Humboldt State University ® Department of Chemistry

Richard A. Paselk

	General Chemistry	Fall 2009
Exercise: Nomenclature	© R. Paselk 2008
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Introduction to Naming; Atoms & Isotopes

Chemical Nomenclature

These exercises are organized into two types, 1) writing formulae and naming them given ions or molecules, and 2) writing formulae given chemical names.

Writing Formulae and Naming Compounds

Note that formulae are generally written with the elements ordered by electronegativity (roughly, elements on the left side of the Periodic table precede those on the right).

You should know about the Stock system of nomenclature for cations and ionic compounds.

• For cations with a single oxidation state (Type I) the name of the element is the name of the cation (no Roman numeral is necessary)
• For cations with more than one oxidation state or charge (Type II) the oxidation number of a cation is indicated by Roman numerals in parenthesis following the symbol with no space, e.g. Fe(III), and the name is then the element name plus the number Fe(III) = iron three = iron(III).

Write the Formulae and names for the simplest compounds made from each of the following pairs of ions:

(Examples 1-10 are answered with explanations, a-j are provided for extra practice - answers only are given.)

1. K+	F-		a. Na+	OH-
2. Al3+	S2-		b. Ga3+	PO43-
3. NH4+	CN-		c. Cu2+	HCO3-
4. Hg22+	C2H3O2-		d. Fe2+	CrO42-
5. Pb2+	SO42-		e. Pb4+	NO3-
6. Sn4+	Cr2O72-		f. Hg22+	I-
7. H+	SO42-		g. H+	PO33-
8. H+	ClO4-		h. H+	NO3-
9. Cs+	NO2-		i. Rb+	OH-
10. Ba2+	O22-		j. Sr2+	O2-

Answers for 1-10

Answers for a-j

Writing Formulae from Names

Note that you can guess the charge on most elemental ions based on their positions on the Periodic table.

• For positive ions the charge is the number of the group for the "A" group (Representative) elements.
  • For representative elements with more than one ion the higher charge will be the group number, the lower will be two lower, e.g. Bi(V) and Bi(III). Note that these ions occur near the bottom of the Periodic table (Periods 5 & 6).
• For negative ions the charge is the group number - 8. Thus for Sulfur in group VI the charge is 6 - 8 = -2.

Write the Formulae for the Binary Ionic Compounds:

1. Sodium chloride
2. Calcium chloride
3. Aluminum sulfide
4. Magnesium iodide
5. Potassium phosphide
6. Zinc oxide
7. Galium selenide
8. Iron(II) nitride
9. Lead(IV) phosphide
10. Mercury(II) selenide
11. Mercury(I) sulfide
12. Tin(II) fluoride

Answers

In addition to these exercises you should familiarize yourself with the text materials and with the Department web pages linked below.

• The Department web page on the names of the elements that you should learn is at:

http://www.humboldt.edu/~chem_dpt/resources/Supplements/element.html

• The common ions and acids and bases you should know are summarized on the Department web pages below:

http://www.humboldt.edu/~chem_dpt/resources/Supplements/IonTable.html & http://www.humboldt.edu/~chem_dpt/resources/Supplements/AcidTable.html

Go to Reflection Questions

© R A Paselk

Last modified 10 September 2009