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Advanced Placement Chemistry
Lesson plan #4
1 class period
Inorganic Nomenclature
Naming Inorganic Compounds
- The names and formulas of compounds are essential vocabulary in chemistry.
- There are now over 13 million known chemical substances. Naming them all would be a hopelessly complicated task if each
had a special name independent of all others.
- The rules for chemical nomenclature are based on the division of substances into different categories.
- The major division is between organic compounds and inorganic ones.
- Organic compounds contain carbon, usually in combination with hydrogen, oxygen, nitrogen, or sulfur.
- All other compounds are called inorganic compounds.
- We will consider three categories of substances:
- Ionic compounds
- Molecular compounds
- Acids
Names and Formulas of Ionic Compounds
- Cations formed from metal atoms have the same name as the metal:
- Na+ sodium ion
- Zn+ zinc ion
- Al3+ aluminum ion
- Ions formed from a single atom are called monatomic ions.
- If a metal can form cations of differing charges, the positive charge is given by a Roman numeral in parenthesis following
the name of the metal:
- Fe2+ iron(II) ion
- Fe3+ iron(III) ion
- Cu+ copper(I) ion
- Cu2+ copper(II) ion
- Ions with different charges exhibit different properties, such as color.
- Cations formed from nonmetal atoms have names that end in -ium:
- NH4+ ammonium ion
- H3O+ hydronium ion
- Monoatomic (one-atom) anions have names formed by dropping the ending of the name of the element and adding the ending
-ide.
- H- hydride ion
- O2- oxide ion
- N3- nitride ion
- A few simple polyatomic anions also have names ending in -ide:
- OH- hydroxide ion
- CN- cyanide ion
- O22- peroxide ion
- Polyatomic (many-atom) anions containing oxygen have names ending in -ate or -ite. These anions are called oxyanions.
The ending -ate is used for the most common oxyanion of an element. The ending -ite is used for an oxyanion that has the same
charge but one less O atom:
- NO3- nitrate
- NO2- nitrite
- SO42- sulfate
- SO32- sulfite
- Prefixes are used when the series of oxyanions of an element extends to four members, as with the halogens. The prefix
per- indicates one more O atom than the oxyanion ending in -ate; the prefix hypo- indicates one less O atom than the oxyanion
ending in -ite:
- ClO4- perchlorate (one more O than chlorate)
- ClO3- chlorate ion
- ClO2- chlorite ion (one less O than chlorate)
- ClO- hypochlorite (one less O than chlorite)
- Notice that if you learn the rules just indicated, you need to know only the name for one oxyanion in a series to deduce
the names for the other members.
- Anions derived by adding H+ to an oxyanion are named by adding as a prefix the word hydrogen or dihydrogen,
as appropriate:
- CO32- carbonate ion
- HCO3- hydrogen carbonate ion
- PO43- phosphate ion
- H2PO4- dihydrogen phosphate ion
- Notice that each H+ reduces the negative charge of the parent anion by one.
- Names of ionic compounds are the cation name followed by the anion name:
- BaBr2 barium bromide
- Al(NO3)3 aluminum nitrate
- Cu(ClO4)2 copper(I) perchlorate (or cupric perchlorate)
Names and Formulas of Acids
- Acids are an important class of hydrogen-containing compounds and are named a special way.
- An acid is defined as a substance whose molecules yield hydrogen ions (H+) when dissolved in water.
- Acids based on anions whose name end in -die.
- Anions whose names end in -ide have associated acids that have the hydro- prefix and an -ic ending as in:
- Cl- (chloride) HCl (hydrochloric acid)
- S2- (sulfide) H2S (hydrosulfuric acid)
- Acids based on anions whose names end in -ate or -ite.
- Anions whose names end in -ate have associated acids with an -ic ending, whereas anions whose names end in -ite have acids
with an -ous ending. Prefixes in the name of the anion are retained in the name of the acid.
- ClO- (hydochlorite) HClO (hypochlorous acid)
- ClO2- (chlorite) HClO2 (chlorous acid)
- ClO3- (chlorate) HClO3 (chloric acid)
- ClO4- (perchlorate) HClO4 (perchloric acid)
Prefixes used in naming binary compounds formed between nonmetals. |
Prefix |
Meaning |
Mono- |
1 |
Di- |
2 |
Tri- |
3 |
Tetra- |
4 |
Penta- |
5 |
Hexa- |
6 |
Hepta- |
7 |
Octa- |
8 |
Nona- |
9 |
Deca- |
10 |
Names and Formulas of Binary Molecular Compounds
- The procedures used for naming binary (two-element) molecular compounds are similar to those used for naming ionic compounds.
- The name of the element farthest to the left in the periodic table is usually written first.
- If both elements are in the same group in the periodic table, the lower one is named first.
- The name of the second element is given an -ide ending.
- Greek prefixes are used to indicate the number of atoms of each element. The prefix mono- is never used with the first
element. When the prefix ends in a or o and the name of the second element begins with a vowel, the a or o is often dropped.
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