Unformatted text preview: It can be seen from Table 1 that most common cations are monatomic. Many elements form
only a single type of monatornic cation. For example, Na+ is the only monatomic cation of
sodium. No compound is known that contains sodium ions with charges greater than plus one.
The cations of elements that form only one type of monatomic cation are given the names of the
elements. For example, Na+ is named the sodium ion. Some elements, such as iron and copper, form two or more different monatomic cations.
Table 1 shows that iron forms Fe2+ and 1363+, while copper forms Cu+ and Cur“. There are two
diﬂ'erent systems for naming cations in cases in which two or more different cations are formed
by an element. The modem system uses Roman numerals to indicate the electron deﬁcits. For
example, Fe2+ is named the iron (H) ion, and Fe3+ is named the iron (Ill) ion. The modern system
is used in Table 1, and it is the one we will use in this course. An older system, which is still in
use, employs stems derived from the Latin names of the elements. For elements that form two
different monatomic cations, the stems are combined with the endings w and i_c to indicate the
ions with the smaller charge and larger charge, respectively. For example, the stem for iron is
fe_rr, and the ions Fe2+ and F e3+ are named the ferrous ion and the m ion, respectively. Many elements form monatomic anions instead of monatomic cations. An example is
chlorine, which forms the Cl‘ ion. Each element that forms monatomic anions forms only a
single type. For example, Cl' is the only monatomic anion formed by chlorine. Monatornic
anions are named by combining a stem formed ﬁom the name of the element with the ending id_e.
For example, Cl' is named the chloride ion. Table 1 contains the names and formulas of several polyatomic ions. The naming of
polyatomic ions is relatively complicated. Consequently, it is probably easier to memorize the
names given rather than consider the set of rules for obtaining them. The names and formulas of ions in Table 1 can be used to obtain the names and formulas of a
large number of ionic compounds. To obtain the formulas of ionic compounds we use the ﬁlm
that all ionic compounds are electrically neutral. Consequently, the formula of any ionic
compound must be such that the sum of the anion and cation charges in the formula unit is Lego.
We also use the fact that the formulas of ionic compounds are simplest formulas only. The
formula unit in an ionic compound is the smallest collection of ions with charges that add to zero. In addition, we use the convention that cations are given before anions in the formulas of
ionic compounds. 24 ...
View Full Document
- Fall '08