Chapter 8 (Chemical Nomenclature)

Interrelationships among polyatomic ion names and formulas

**MEMORIZE COMMON POLYATOMIC NAMES AND FORMULAS PLUS A FEW NON COMMON (JUST IN CASE). 1. Most of the ions have a negative charge (-1 to -3). Only two positive ions are listed in the table: ammonium and hydronium. 2. Four of the poly ions have names ending in -ide: hydroxide, cyanide, azide, and peroxide. This represents the rule that the suffix -ide is only for monoatomic ions. 3. A number of -ate, -ite pairs of ions exist, for example sulfate and sulfite. The ion with the higher number of oxygens is always -ate; the -ite ion always contains one less oxygen than the -ate ion. 4. A number of pairs of ions exist where one member of the pair differs from the other by having a hydrogen atom present, for example, carbonate, and hydrogen carbonte or bicarbonate. The charge of the hydrgogen containing ion is always one less than the charge on the other ion. 5. Two pairs of ions exist in which the difference between pair members is that a sulfur atom has replaced an oxygen atom in one member of the pair (SO_4^2- and S_2O_3^2-)(OCN^- and SCN^-).

General rules to follow when naming compounds

1) Compounds resulting from the combination of a metal and one or more nonmetals is considered ionic. 2) Compounds resulting from combinations of a nonmetal with other nonmetals are considered molecular. 3) Metalloids are considered to be nonmetal for nomenclature purposes. Exception to these rules: when a positive polyatomic ion is present. In this condition, it is considered to act just like a metal that is positively charged, even though it is made up of nonmetals. (Example: considered the ion HH_4^+; NH_4Cl---no metals are present but it is still ionic.)

Reasoning pattern when deciding which method of nomenclature to use:

1) Decide, first, whether the compound is ionic or molecular. If a metal or polyatomic ion is present, the compound is ionic. If not, the compound is molecular. 2) If the compound is ionic, then classify it as binary ionic or polyatomic-ion-containing ionic and use rules that appropriate for that classification. 3) If the compound is molecular, classify it as an acid or nonacid. An acid must have the element hydrogen present (written first in the chemical formula), and the compound must be in water solution. If the compound is a nonacid, name it according to the rules for binary molecular compounds. ***Refer to figure 8.9 for illustration of the decision tree

Binary ionic compounds may be divided into two categories

1) Fixed-charge 2) Variable-charge

The names of binary ionic compounds guidelines

1) Fixed-charge metal ions take the full name of the element plus the word "ion." -Example: Na^+ -- sodium ion 2) Variable-charge metal ions take the full name of the element followed by a roman numeral (in parentheses) that gives the ionic charge plus the word "ion." Example: Fe^2+ = iron(II) ion Fe^3+ = ion(III) ion Cu^2+ = copper(II) ion **Roman numerals are never a part of the formula, but always a part of the name. 3) Nonmetal ions take the stem of the name of the element followed by the suffix -ide plus the word "ion." -Example: Cl^- chloride ion S^2- sulfide ion Refer to figure 8.3

Not all polyatomic-ion-containing compounds are ternary

1) Some can contain four when both ions present are polyatomic. Although if the two ions share an element then there are only three elements. 2) A poly ion can contain three elements and cause the number of elements to be four. 3) Binary ionic compounds can occur with two polyatomic ions present. In this case, the poly ions would be homoatomic and the other ion would be monoatomic. Ultimately, this does not affect the nomenclature of these compounds. Same rules for ionic compound naming apply. Refer to figure 8.4 for generalization and illustration of ionic compound naming

Binary compound

Contains only two elements. The term binary means "two."

Binary ionic compound

Contains two elements--one is a metal and the other is a nonmetal.

Naming acids

Derived from the names of the negative ions produced from the acids interaction with water. *Refer to figure 8.6 and figure 8.7

Naming a variable-charge binary ionic compound, given the formula:

First word: name of metal + roman numeral Second word: stem of name of nonmetal + -ide Example: CuO Cu charge + O charge = 0 Oxide ion = -2 charge. Cu charge = x. Therefore, x + (-2) = 0 --- solve algebraically x = 2 Thus, Cu ions are Cu^2+, and the name is: Copper(II) oxide.

How to recognize an acid based on its formula

Hydrogen is written first in the formula.

Names for fixed-charge binary ionic compounds are assigned using the following rule:

The full name of the metallic element is given first, followed by a separate word consisting of the stem of the nonmetallic element name and the suffix -ide. Example: NaF -- Sodium Flouride

Names for variable-charge binary ionic compounds are assigned using the following rule:

The full name of the metallic element with a roman numeral appended to it is given first, followed by a separate word consisting of the stem of the nonmetallic element name and the suffix -ide. Example: two different iron chloride molecules exist-- one contains Fe^2+ and the other Fe^3+. The names, respectively, are iron(II) chloride and iron(III) chloride.

Naming of binary molecular compounds

The name of the first nonmetal is used in full, followed by a separate word containing the stem of the name of the second nonmetal and the suffix -ide. Numerical prefixes giving numbers of atoms present, precede the names of both nonmetals. When hydrogen is first in formula don't give it a prefix, because you treat it as a metal. The prefix mono- is always dropped at the start of a name. Refer to table 8.5 and figure 8.5

Order of nonmetals in formula

The order of the formula components parallels increasing nonmetallic character. Basically, the element with the most metallic character goes on the left. Order: B, Si, C, Sb, As, P, N, H, Te, Se, S, I, Br, Cl, O, F. From left to right. Section 8.6.

Older method for indicating the charge on a variable-charge metal ion

Uses suffixes rather than roman numerals. When a metal has two common ionic charges, the suffix -ous is used for the ion of lower charge, and the suffix -ic for the ion of higher charge.

-ate rule for acid names

When the negative ion name produced ends in -ate the acid name has three parts: 1) the name of the negative ion less the -ate ending 2) the suffix -ic 3) the word acid Example: HNO_3 (nitrate) is named nitric acid

-ite rule for acid names

When the negative ion name produced ends in -ite the acide name has three parts: 1) the name of the negative ion less the -ite ending 2) the suffix -ous 3) the word acid Example:HClO (hypochlorite) is named hypochlorous acid

-ide rule for acid names

When the negative ion produced ends in -ide the acid name has four parts: 1) the prefix hydro- 2) the stem of the name of the negative ion 3) the suffix -ic 4) the word acid Example: HCl (chloride) is name hydrochloric acid

Ternary compound

a compound containing three different elements. Some polyatomic-ion-containing compounds are ternary, for example. If they contain a monoatomic and polyatomic ion (two).

Fixed-charge metal

a metal that only forms one type of positive ion, such as potassium[+] and aluminum[3+], in which each metal has a consistent charge magnitude. Memorize the fixed-charge elements (only 15)

Binary molecular compound

a molecular compound in which only two nonmetallic elements are present.

Nomenclature for ionic compounds containing polyatomic ions

basically the same as that of binary ionic compounds with only two considerations: 1) If the polyatomic ion is positive, its name is substituted for that of the metal. 2) If the polyatomic ion is negative, its name is substituted for the nonmetal stem plus -ide. In the case where both components are poly ions, dual substitution occurs and the resulting name includes just the names of the poly ions. Refer to example 8.7

Acid

is a hydgrogen-containing molecular compound whose molecules yield hydrogen ions (H^+) when dissolved in water. An acid is a molecular compound--no ions are present.

Variable-charge metal

is a metal that forms more than one type of positive ion, with the ion types differing in charge magnitude. For example, the element iron sometimes forms an Fe^2+ ion and at other times an Fe^3+ ion. Most metals are variable-charge metals.

Nonoxyacid

is a molecular compound composed of hydrogen and one or more nonmetals other than oxygen that produce H^+ ions in an aqueous solution. All common nonoxyacids, with the exception of HCN, are binary compounds. Exist as pure compounds and water solutions (Refer to table 8.7).

Ternary molecular compound

is a molecular compound that contains three different nonmetallic elements. Oxyacids are ternary.

Oxyacid

is a molecule compound composed of hydrogen, oxygen, and one or more other elements that produces H^+ ions in an aqueous solution.

Ternary ionic compound

is an ionic compound in which three elements are present, one element in a monoatomic ion and two elements in a polyatomic ion.

Common name

name not based on IUPAC rules.

Systematic name

name of compound based on IUPAC rules that conveys information about the compound.

Names of oxyacids in a series

related to the -ic acids by affixes as follows: 1) An oxyacid containing one less (n - 1) oxygen atom than the -ic acid is the -ous acid. 2) An oxyacid containing two fewer (n - 2) oxygen atoms than the -ic acid is the hypo-______-ous acid. 3) An oxyacid containing one more (n + 1) oxygen atom than the -ic is the per-______-ic acid. ***Refer to figure 8.8 for supplementary illustration (period 2 - 3 oxygens and charge increases from left to right; period 3 - 4 oxygens and charge increases in the same manner)

The charge neutrality principle

the total negative charge and the total positive charge must add to zero.