The Nomenclature of Inorganic Substanc

The Nomenclature of Inorganic Substance

You will meet compounds in this text and will learn their name as you go along.

However, it is useful from the outset to know something about how to form their

names. Many compounds were given common names before their compositions were

known. Common names include water, salt, sugar, ammonia, and quartz. A systematic

name, on the other hand, reveals which elements are present and,in some cases, how

their atoms are arranged.The systematic name of table salt, for instance,is sodium

chloride, which indicates at once that it is a compound of sodium and chlorine. The

systematic naming of compounds, which is called chemical nomenclature, follows a

set of rules, so that the name of each compound need not be memorized, only the

rules.

Names of Cations

The names of monatomic cations are the same as the name of the element, with

the addition of the word ion, as in sodium ion for Na+. When an element can form

more than one kind of cation, such as Cu+ and Cu2+ from copper, we use the Stock

number, a Roman numeral equal to the charge of the cation. Thus, Cu+ is a copper (Ⅰ)

ion and Cu2+ is a copper (Ⅱ) ion. Similarly, Fe2+ is an iron (Ⅱ) ion and Fe3+ is an iron

(Ⅲ) ion. Most transition metals form more than one kind of ion, so it is usually

necessary to include a Stock number in the names of their compounds.

An older system of nomenclature is still in use. For example, some cations were

once denoted by the endings –ous and –ic for the ions with lower and higher

charges, respectively. In this system, iron (Ⅱ) ions are called ferrous ions and iron (Ⅲ)

ions are called ferric ions.

Names of Anions

Monatomic anions are named by adding the suffix –ide and the word ion to the

first part of the name of the element ( the “stem” of its name ). There is no need to

give the charge, because most elements that form monatomic anions form only one

kind of ion.The ions formed by the halogens are collectively called halide ions and

include

fluoride (F-), chloride (Cl-), bromide (Br-), and iodide ions (I-).

The names of oxoanions are formed by adding the suffix –ate to the stem of the

name of the element that is not oxygen, as in the carbonate ion, CO32-. However,

many elements can form a variety of oxoanions with different numbers of oxygen

atoms; nitrogen, for example, forms both NO2- and NO3-. In such cases, the ion with

the larger number of oxygen atoms is given the suffix –ate, and that with the smaller

number of oxygen atoms is given the suffix –ite. Thus, NO2- is nitrate and NO3- is

nitrite.

Some elements-particularly take for the halogens—form more than two oxoanions.

The name of the oxoanion with the smallest number of oxygen atoms is formed by

adding the prefix hypo- to the –ite form of the name, as in the hypochlorite ion,

ClO-. The oxoanion with a higher number of oxygen atoms than the –ate oxoanion

is named with the prefix per- added to the –ate form of the name.

An example is the perchlorate ion, ClO4-. Some anions include hydrogen, such as HS- and HCO3-. The names of these

anions begin with “hydrogen”. Thus, HCO3- is the hydrogen carbonate ion.In an

older system of nomenclature, an anion containing a hydrogen atom was named with

the prefix bi-, as in bicarbonate ion for HCO3-.

The oxoacids are molecular compounds that can be regarded as the parents of the

oxoanions. The formulas of oxoacids are derived from those of the corresponding

oxoanions by adding enough hydrogen ions to balance the charges. This procedure is

only a formal way of building the chemical formula, because oxoacids are all

molecular compounds.

For example, the sulfate ion, SO42-, needs two H+ ions to cancel its negative

charge, so sulfuric acid is the molecular compound H2SO4.Similarly, the phosphate

ion, PO43-, needs these H+ ions, so its parent acid is the molecular compound H3PO4,

phosphoric acid.As these examples illustrate, the names of the parent oxoacids are

derived from those of the corresponding oxoanions by replacing the –ate suffix with

–ic acid. In general, -ic oxoacids are the parents of –ate oxoanions and –ous

oxoacids are the parents of –ite oxoanions.

Names of Ionic Compounds

An ionic compound is named with the cation name first, followed by the name of

the anion;the word ion is omitted in each case. Typical names include potassium

chloride (KCl),a compound containing K+ and Cl- ions, and ammonium nitrate

(NH4NO3), which contains NH4+ and NO3- ions. The copper chloride that contains

Cu+ ions (CuCl) is called copper (Ⅰ) chloride, and the chloride that contains Cu2+