http://www.ck12.org Chapter 7. Chemical Nomenclature
TABLE7.1:(continued)
1+ 2+ 3+ 3- 2- 1-
rubidium, Rb+ strontium, Sr^2 + telluride, Te^2 − iodide, I−
cesium, Cs+ barium, Ba^2 +Transition Metal Ions
Most transition metals differ from the metals of Groups 1, 2, and 13 in that they are capable of forming more than one
type of stable cation. For example, iron sometimes loses two electrons to form the Fe^2 +ion, but it is also common
for iron to lose three electrons to form the Fe^3 +ion. Although they are members of the p block and not the d block,
tin and lead also form more than one type of ion. Because the charges of these ions cannot simply determined by
looking at the periodic table, they must have names that also indicate their charge. The Stock system, proposed by
Alfred Stock (1876-1946), denotes the charge of these ions by using a Roman numeral in parentheses after the name
of the ion. For example, the previously mentioned iron ions are named the iron (II) ion and the iron (III) ion. When
said out loud, "iron (II) ion" should be read, “iron two ion.”Table7.2 lists the names and formulas of some of the
more common transition metal ions:
TABLE7.2: Common Transition Metal Ions
1+ 2+ 3+ 4+
copper (I), Cu+ cadmium, Cd^2 + chromium (III), Cr^3 + lead (IV), Pb^4 +
gold (I), Au+ chromium (II), Cr^2 + cobalt (III), Co^3 + tin (IV), Sn^4 +
silver, Ag+ cobalt (II), Co^2 + gold (III), Au^3 +
copper (II), Cu^2 + iron (III), Fe^3 +
iron (II), Fe^2 +
lead (II), Pb^2 +
manganese (II), Mn^2 +
mercury (II), Hg^2 +
nickel (II), Ni^2 +
platinum (II), Pt^2 +
tin (II), Sn^2 +
zinc, Zn^2 +Notice inTable7.2 that there are three cations whose names do not include a Roman numeral. Silver, cadmium, and
zinc only form one common type of ion, so the charges on ions of these elements are considered to be implied by the
name (1+ for silver, and 2+ for zinc and cadmium). By convention, the Stock system is not used for these elements,
and their cations are named in the same way as those of the representative elements.
There is also an older system for naming some of these cations that is still occasionally used. The Latin root of the
metal name is written with one of two suffixes: (1)–icfor the ion with a higher charge, and (2)–ousfor the ion
with a lower charge. For example, the Latin name for iron is ferrum, so the Fe^3 +ion is called the ferric ion, and the
Fe^2 +ion is called the ferrous ion. The primary disadvantage of this system is that the suffixes do not tell you exactly
what the charge is for a given ion. For copper, the two most common charges are 1+ and 2+, so Cu^2 +is called the
cupric ion and Cu+is the cuprous ion. The Stock system is a much more informative system and will be used as the
primary method for naming transition metal compounds throughout this book.
Example 7.1
What are the names of the following compounds?
- CuCl (composed of Cu+and Cl−)