Naming compounds writing formulas from names

Atoms and their symbols were introduced in Chap. 3 and 1. In this chapter, the representation of compounds by their formulas will be developed. The formula for a compound (Sec. 4.3) contains much information of use to the chemist. We will learn how to calculate the number of atoms of each element in a formula unit of a compound. Since atoms are so tiny, we will learn to use large groups of atoms—moles of atoms—to ease our calculations. We will learn to calculate the percent by mass of each element in the compound. We will learn how to calculate the simplest formula from percent composition data, and to calculate molecular formulas from simplest formulas and molecular weights. The procedure for writing formulas from names or from knowledge of the elements involved will be presented in Chaps. 5. ft. and 13. 

Rules for writing formulas from names will also be presented. An outline of the classes that wiU be presented is given in Table 6-1, and rules for naming compounds in the different classes are illustrated in Fig. 6-1. These summaries are available if you want them, but they are not the only way to remember the varioup systems. Use either one or the other if you wish, but not both. 

Name five metals and five nonmetals that are very likely to form ionic compounds. Write formulas for compounds that might result from the combination of these metals and nonmetals. Name these compounds. 

WRITING FORMULAS FROM NAMES OF IONIC COMPOUNDS 103... 

Writing Formulas from Names of Ionic Compounds... 

Writing Formulas from the Names of Molecular Compounds... 

Guide to Writing Formulas from the Name of an Ionic Compound... 

Writing formulas from names Given the name of a molecular compound, you can write its formula by analyzing the name in terms of the rules given above. Use the prefixes that indicate number mono-, di-, and so on) to write the proper subscripts. 

Phosphorus lies to the left and below oxygen in the periodic table, so it is named first. According to the rules, the name is phosphorus pentoxide, and professional chemists call this compound phosphorus pentoxide. (Some texts for beginning students call the compound diphosphorus pentoxide, to aid students in writing the formula from the name.)... 

Reversing this procedure will allow us to write a formula from a name. Let s try this with carbon tetrachloride and oxygen difluoride. The formulas for these two compounds are CCLt and OF2, respectively. 

To write the formula from the name of a binary compound containing only nonmetals, simply write the symbols for the separate atoms with the prefixes converted to subscripts. 

The charges on the ions allow us to deduce the formula from the name of a compound, even though the numbers of each type of ion are not stated in the name. Writing formulas for ionic compounds requires deducing how many of each type of ion must be present to have a neutral compound (see Section 5.2). 

In writing formulas for ionic compounds from their names, we must remember the rules from Chapter 5. Be sure to balance the number of positive and negative charges The charges on the cations are implied for some cations (the constant type) and stated explicitly in the name for the others. The charge on a monatomic anion is equal to the group number minus 8 (see Section 5.2). 

Now let s go the other way and convert from systematic names to chemical formulas. The first step in writing formulas when given the systematic name of a binary covalent compound is to recognize the name as representing a binary covalent compound. It will have one of the following general forms. 

Follow these steps for writing formulas for binary covalent compounds when you are given a systematic name. Notice that they are the reverse of the steps for writing names from chemical formulas. 

As we noted earlier, chemists have established different sets of rules for writing the names and formulas of different types of chemical compounds, so the first step in writing a name from a chemical formula is to decide what type of compound the formula represents. A chemical formula for an ionic compound will have one of the following forms. 

Before you can write a chemical formula from the name of a compound, you need to recognize what type of compound the name represents. For binary ionic compounds, the first part of the name is the name of a metallic cation. This may include a Roman numeral in parentheses. The anion name starts with the root of the name of a nonmetal and ends with -ide. 

Doing the reverse, writing a formula from the name of a compound, requires knowing the meaning of the numerical prefixes and the stems of the elements. Examine these examples to follow the logic from name to formula ... 

Write formulas for and name the binary hydrogen compounds of the second-period elements (Li to F). Describe how the physical and chemical properties of these compounds change from left to right across the period. 

Note in some of fhe following problems, you will need to write a chemical formula from the name of the compound. It may help to review Chapter 4. 

So far we have learned how to name a compound by examining its structural formula. We must also be able to do the reverse to write the stmctural formula from the name. 

Because chemists around the world need to be able to communicate with one another, they have developed a set of rules for naming compounds. Using this standardized naming system, you can write a chemical formula from a compound s name and name a compound given its chemical formula. 

Sodium chloride is not the only ionic compound that forms from sea water. Identify four other compounds that could be formed that contain the sodium ion. Write both the formula and the name for each compound. 

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