Writing Formulas from Names

Remember, to name a compound from its formula, write the name of the positive ion (cation) first, followed by the name of the anion (negative ion). So Li2S is lithium sulfide. 

Questions 51 to 80 Items in the remaining questions are selected at random from various sections of the chapter. Unless marked with an asterisk ( ), all names and formulas are included in the Goals and should be found with reference to no more than a periodic table. Ions in compounds marked with an asterisk are included in Tables 6.7 and 6.8, or, if the unfamiliar ion is monatomic, the atomic number of the element is given. In all questions, given a name, write the formula given a formula, write the name. 

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. 

Predicting Magnesium reacts with both oxygen and nitrogen from the air at the high temperature of the crucible. Predict the binary formulas for both products. Write the names of these two compounds. 

When you write a chemical formula that involves polyatomic ions, you treat them just like other ions. You still need to balance charges to form a neutral atom. We re sorry to report that when you re converting from a formula to a name, you can t use any simple rule for naming polyatomic ions. You just have to memorize the entire table of polyatomic ions and their charges. 

The systematic name of a compound is designed so that one may deduce from it the molecular structure of the compound, as indicated by its graphic formula. In other words, it is essentially a verbal substitute for the graphic formula and, in its most elaborate form, provides precisely the same structural information. However, it is a poor substitute most chemists if required to indicate the structure of a compound would draw the formula rather than write the name. Similarly, a systematic name is not often readily understood until it has been translated into its graphic equivalent. Inevitably, systematic names tend to be long, and ill-adapted for use in conversation they are useful only when to employ the graphic form would be impossible or inconvenient. 

In working with formulas for nonmetals, notice that there is no balancing of charges as was the case for metal and nonmetal combinations. You will know the formula from its name, such as carbon dioxide. You will also be able to write the name if you know the formula. 

Answer Notice how the arrows crisscross as they move toward the subscript position. That is where the name comes from. The method makes formula writing for ionic compounds quick and easy. There is one thing you need to pay attention to as you use this method, as the next example will demonstrate. 

What is the molecular formula and the name of the hydrocarbon that is obtained from the reaction of 2-iodobutane with an excess amount of sodium metal Write out the reaction and explain. 

Sections 6.2 and 6.3 for writing formulas from names and Sections 8.2 and 8.4 to complete and balance the equation. 

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. 

One of the most important requirements of chemistry is communicating information to others. Chemists discuss compounds by using both chemical formulas and names. The chemical formula and the name for the compound must be understood universally. Therefore, a set of rules is used in the naming of compounds. This system of naming allows everyone to write a chemical formula when given a compound name and to name the compound from a given chemical formula. 

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. 

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. 

Write the name and formula for the compound formed from sodium ions and nitrite ions. 

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. 

Writing structural formulae from names of alkanes... 

If you are having trouble writing formulas from names, review the appropriate sections of Chapter 5. It is very important that you are able to do this. 

Writing Formulas from Names 134 Chapter Review 135... 

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