Prefixes molecular compounds

Binary molecular compounds are named by using Greek prefixes to indicate the number of atoms of each element present the element named second has its ending changed to -ide. 

Naming molecular compounds uses Greek prefixes to indicate the number of... 

Prefixes precede each element to indicate the number of atoms in the molecular compound. The stem of the second element is used with the ide suffix. The prefix mon is dropped for the initial element, that is, if no prefix is given, it is assumed the prefix is one. Examples of molecular com-... 

Knowing the names of the elements and a few basic rules allows us to name simple compounds given the chemical formula. We also can reverse the process. That is, if we know the name of the compound, we should be able to write the chemical formula. The process is straightforward for molecular compounds because prefixes are included in the names. Hence, the formula for sulfin dioxide is SO and carbon monoxide is CO. 

Molecular compound names clearly specify how many of each type of atom participate in the compound. Table 6-2 lists the prefixes used to do so. 

You can attach the prefixes in Table 6-2 to any of the elements in a molecular compound, as exemplified by SO3 (sulfur trioxide) and N2O (dinitrogen monoxide). The second element in each compound receives the -ide suffix, as in ionic compounds (which we discuss earlier in this chapter). In the case of molecular compounds, where cations or anions aren t involved, the more electronegative element (in other words, the element that s closer to the upper right-hand corner of the periodic table) tends to be named second. 

Note that the absence of a prefix from the first named element in a molecular compound implies that there s only one atom of that element. In other words, the prefix mono- is unnecessary for the first element only. You still have to attach a mono- prefix, when appropriate, to the names of subsequent elements. 

A. Dinitrogen monoxide, sulfur hexafluoride, and dichlorine octoxide. Notice that none of these compounds contain any metals, which means that they re most certainly molecular compounds. The first compound contains two nitrogen atoms and one oxygen atom, so it s called dinitrogen monoxide. The second compound contains one sulfur and six fluorines. Because sulfur is the first named element, you don t need to include a mono- prefix. You simply name the compound sulfur hexafluoride (rather than monosulfur hexafluoride ). Using the same methods, the third compound is named dichlorine octoxide. 

Many simple inorganic molecular compounds are named by using the Greek prefixes in Table D.2 to indicate the number of each type of atom present. Usually, no prefix is used if only one atom of an element is present an important exception to this rule is carbon monoxide, CO. Most of the common binary molecular compounds—molecular compounds built from two elements—have at least one element from Group 16 or 17. These elements are named second, with their endings changed to -ide ... 

Because nonmetals often combine in different proportions to form different compounds, numerical prefixes are usually included in the names of binary molecular compounds to specify the numbers of each kind of atom present. The... 

Ionic Compounds To name an ionic compound, you just name the cation and then the anion. There is a crucial difference between naming ionic compounds and molecular compounds. In molecular compounds you must include prefix multipliers (di, tri, etc.) to indicate the number of each kind of atom in the molecule. In ionic compounds you must not include prefix multipliers, because the number of each ion in the formula unit is controlled by the charges on the ions. If the cation is a representative element, it is not necessary to indicate the charge, because (with few exceptions) these metals form cations with an ionic charge equal to the group number. 

Water molecules often occupy positions within the lattice of an ionic crystal. These compounds are called hydrates, and the water molecules are known as water of hydration. The water of hydration is added after a centered dot in a formula. In a name, a number-prefix (listed below for molecular compounds) indicating the number of water molecules is followed by the root -hydrate. 

Molecular compounds (compounds making up molecules with a neutral charge) are usually composed entirely of nonmetals and are named by placing the less electronegative atom first. See Skill 3.3 for the relationship between electronegativity and the periodic table. The suffix -ide is added to the second, more electronegative atom, and prefixes indicating numbers are added to one or both names if needed. 

When determining the name of a molecular compound from the formula, the subscript determines the prefix you will use in the name. 

Molecular compounds are named using the elements names, a system of prefixes, and -ide as the ending for the second element in the compound. 

Names of covalent molecular compounds include prefixes that tell the number of each atom present. 

For binary molecular compounds (compounds with only two elements), the name begins with the name of the element that is farthest to the left and lowest in the periodic table. The name of the second element is given the suffix -ide and a Greek number prefix is used on the first element if necessary (e.g., dinitrogen tetroxide, N204). 

A few other rules are helpful when naming molecular compounds. If only one atom of the first element is listed, the prefix mono is usually omitted. Also, if the vowel combinations 0-0 or a-o appear next to each other in the name, the first of the pair is omitted to simplify pronunciation. Thus, mononitrogen monooxide, NO, becomes nitrogen monoxide. 

To write the formula of a molecular compormd for which you are given the name, first write the symbols of each element in the order given in the name. Then add the appropriate subscript after each element that has two or more atoms present. Remember that the prefixes in the name teU how many atoms of each element are present. For example, the compound sulfur hexafluoride contains the elements sulfur and fluorine. Because the word sulfur has no prefix, it is understood that there is only one sulfur atom thus, the symbol S does not require a subscript. The prefix hexa tells you that six fluorine atoms are in the compound, so the subscript 6 must be added to the F. The formula for sulfur hexafluoride is SFg. Follow the rules for writing a formula for a molecular compound as you examine the formula shown in Figure 5.17. 

Binary molecular compounds are named by writing the two elements in the order they are found in the formula, changing the ending of the second element to -ide, and adding Greek prefixes to the element names to indicate how many atoms of each are present. 

TABLE 2.4 Greek Prefixes Used in Naming Molecular Compounds... 

Exceptions to the use of Greek prefixes are molecular compounds containing hydrogen. Traditionally, many of these compounds are called either by their common, nonsystematic names or by names that do not specifically indicate the number of H atoms present ... 

Nearly all binary molecular compounds involve two nonmetals bonded together. Although many nonmetals can exhibit different oxidation numbers, their oxidation numbers are not properly indicated by Roman numerals or suffixes. Instead, elemental proportions in binary covalent compounds are indicated by using a prefix system for both elements. The Greek and Latin prefixes for one through ten are mono, di, tri, tetra, penta, hexa, hepta, octa, nona, and deca. The prefix mono- is omitted for both elements except in the common name for CO, carbon monoxide. We use the minimum number of prefixes needed to name a compound unambiguously. The final a in a prefix is omitted when the nonmetal stem begins with the letter o we write heptoxide, not heptaoxide. ... 

I Names of covalent molecular compounds include prefixes for the number of each atom present. The final letter of the prefix Is dropped If the element name begins with a vowel. 

Strategy When writing formulas of molecular compounds, the prefixes specify the number of each type of atom in the compound. 

Although hydrocarbons are binary molecular compounds, they are not named like the binary inorganic compounds discussed in Section 2.8. Instead, each alkane has a name that ends in -ane. The alkane with four carbons is called butane. For alkanes with five or more carbons, the names are derived from prefixes like those in Table 2.6. An alkane with eight carbon atoms, for example, is octane (CsHig), where the octa- prefix for eight is combined with the -ane ending for an alkane. 

When there is more than one possible combination of two elements, the number of atoms of a given type in the compound is designated with a prefix such as mono-, dir, tri-, tetra-, and so on. Table 5.4 lists the prefixes for up to ten atoms, and some common molecular compounds and their names are given in Table 5.5. 

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