Names and Formulas of Some Ionic Compounds

It Is very Important to learn the names, formulas, and charges of the common polyatomic Ions listed In Table 2-2 and recognize them In chemical formulas. 

The names of some common ions appear in Table 2-2. You will need to know the names and formulas of these frequendy encountered ions. They can be used to write the formulas and names of many ionic compounds. We write the formula of an ionic compound by adjusting the relative numbers of positive and negative ions so their total charges cancel (i.e., add to zero). The name of an ionic compound is formed by giving the names of the ions, with the positive ion named first. 

Ionic compounds (clockwise, from top, salt (sodium chloride, NaCi), caicite (calcium carbonate, CaCOg), cobalt(II) chioride hexahydrate (C0CI2 6H2O), fluorite (calcium fluoride, CaF2). 

Unless otheiwise noted, all content on this page is Cengage Learning. 

You may not be sure of the best point to start learning the naming of compounds. It has been found that before rules for naming can make much sense or before we can expand our knowledge to more complex compounds, we need to know the names and formulas in Tables 2-1 and 2-2. If you are unsure of your ability to recall a name or a formula in Tables 2-1 and 2-2 when given the other, prepare flash cards, hsts, and so on that you can use to learn these tables. 

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Atoms and Molecules 2-2 Chemical Formulas 2-3 Ions and Ionic Compounds 2-4 Names and Formulas of Some Ionic Compounds 2-5 Atomic Weights 2-6 The Mole... 

Combine simple ions to write formulas and names of some ionic compounds... 

Hydrates Some ionic compounds incorporate a fixed number of water molecules into their formula unit. The compound that contains the water is called a hydrate, and removal of the water affords the anhydrous salt. Compounds that have a strong tendency to absorb water are called hygroscopic. To name a hydrate, you simply name the ions and then add the appendage hydrate, along with a multiplier to indicate the number of water molecules in the formula. 

Once we know how to name both of the ions, an ionic compound is named simply by combining the two names. The cation is listed first in the formula unit and in the name. Example Problem 2.6 provides some examples of the way to determine the name of an ionic compound. 

Some ionic compounds—such as NaCl (table salt) and NaHCOs (baking soda)— have common names, which are nicknames of sorts learned by familiarity. However, chemists have developed systematic names for different types of compounds including ionic ones. Even if you are not familiar with a compound, you can determine its systematic name from its chemical formula. Conversely, you can deduce the formula of a compound from its systematic name. 

The word nomenclature simply means naming. You have already seen some chemical formulas such as NaCl, H20, and H2S04. There are many times when having names for chemicals is more convenient than having their formulas. Chemical naming falls into two main groups that for ionic compounds formed of positive and negative ions, and that for nonionic compounds. 

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). 

Metal -nonmetal compounds and ammonium compounds (containing the NH4 group within a formula) are ionic. Other compounds are covalent, except that acids are ionized, some completely, when dissolved in water. The acids are named with a special system of their own, but pure binary acids can be named similarly to alkali metal-nonmetal compounds. 

Some stable ionic compounds are capable of bonding to a certain number of molecules of water per formula unit. Thus, copper(II) sulfate forms the stable CuSO4-5H2O, with five molecules of water per CaiSO, unit. This type of compound is called a hydrate. The name of the compound is the name of the anhydrous (without water) compound with a designation for the number of water molecules appended. Thus, CaiS( ),-5I t,() is called copper(II) sulfate pentahydrate. The 5 multiples everything after it until the next centered dot or the end of the formula. Thus, included in CuSO4-5H2O are ten H atoms and nine O atoms (five from the water and four in the sulfate ion). 

Seawater contains many dissolved substances, mostly dissolved sodium chloride. In Chapter 4, you learned that sodium chloride is an ionic compound. Another ionic compound found dissolved in seawater is magnesium chloride. Some common ionic compounds used in everyday life are potassium chloride, a salt substitute used by people avoiding sodium for health reasons potassium iodide, added to table salt to prevent iodine deficiency and sodium fluoride, added to many toothpastes to strengthen tooth enamel. You will learn how to use the language of chemistry to name and write the formulas of ionic compounds. 

Unlike ionic compounds, molecular compounds contain discrete molecular units. They are usually composed of nonmetallic elements (see Figure 2.8). Many molecular compounds are binary compounds. Naming binary molecular compounds is similar to naming binary ionic compounds. We place the name of the first element in the formula first, and the second element is named by adding -ide to the root of the element name. Some examples are... 

We need to learn how to properly name and write formulas for ionic and covalent compounds. We should become familiar with some of their properties and be able to relate these properties to the structure and bonding of the compounds. 

Compounds Formed from Polyatomic Ions Ionic compounds in which one or both of the ions are polyatomic are very common. Table 2.5 gives the formulas and the names of some common polyatomic ions. Remember that the polyatomic ion stays together as a charged unit. The formula for potassium nitrate is KNO3 each balances one N03. The formula for sodium carbonate is Na2C03 two Na balance one CO-. When two or more of the same polyatomic ion are... 

The formulas and names of some common polyatomic ions are given in I Table 4.7. From this information, the formulas and names for compounds containing polyatomic ions can be written. The rules are essentially the same as those used earlier for binary ionic compounds. In the formulas, the metal (or ammonium ion) is written first, the positive and... 

Since there are so many different compounds, chemists have developed systematic ways to name them. If you learn these naming rules, you can examine a compound s formula and determine its name or vice versa. Many compounds also have a common name. For example, Ff20 has the common name water and the systematic name dihydrogen monoxide. A common name is like a nickname for a compound, used by those who are familiar with it. Since water is such a familiar compound, everyone uses its common name and not its systematic name. In the sections that follow, you will learn how to systematically name simple ionic and molecular compounds. Keep in mind, however, that some compmmds also have common names that are often used instead of the systematic name. Common names can be learned only through familiarity. 

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