Chemical formulas of ionic compounds

C02-0072. Nitrogen forms a few compounds in which it exists as an anion with - 3 charge. What are the chemical formulas of ionic compounds that form between nitrogen and (a) sodium (b) magnesium ... 

Here are some specific examples illustrating chemical formulas of ionic compounds. 

The formulas of ionic compounds have a different meaning from those of molecular compounds. Each crystal of sodium chloride has a different total number of cations and anions. We cannot simply specify the numbers of ions present as the formula of this ionic compound, because each crystal would have a different formula and the subscripts would be enormous numbers. However, the ratio of the number of cations to the number of anions is the same in all the crystals, and the chemical formula shows this ratio. In sodium chloride, there is one Na+ ion for each Cl ion so its formula is NaCl. Sodium chloride is an example of a binary ionic compound, a compound formed from the ions of two elements. Another binary compound, CaCl2, is formed from Ca2+ and Cl- ions in the ratio 1 2, which is required for electrical neutrality. 

Formulas of Ionic Compounds As we mentioned earlier, compounds (like atoms) must be electrically neutral. The net charge on an ionic compound must be zero. When a metal gives its electrons away to form a cation, there has to be some other species, often a nonmetal, present to accept the electrons. Thus, whenever a cation is forming, there is also a concurrent formation of an anion. Chemical systems have to remain electrically neutral. 

To assign a chemical formula of a compound from its name, you first must recognize whether the compound is ionic or molecular. For ionic compounds, you must also know the charges on the ions. 

You have seen how Lewis structures can help you draw models of ionic, covalent, and polar covalent compounds. When you draw a Lewis structure, you can count how many electrons are needed by each atom to achieve a stable octet. Thus, you can find out the ratio in which the atoms combine. Once you know the ratio of the atoms, you can write the chemical formula of the compound. Drawing Lewis structures can become overwhelming, however, when you are dealing with large molecules. Is there a faster and easier method for writing chemical formulas ... 

Use the principle of charge balance and Lewis diagrams to write chemical formulas for ionic compounds (Section 3.6, Problems 21-24). 

An ionic compound used as a chemical fertilizer has the composition (by mass) 48.46% O, 23.45% P, 21.21% N, 6.87% H. Give the name and chemical formula of the compound and draw Lewis diagrams for the two types of ions that make it up. 

Types of Chemical Bonds electronegativity Bond Polarity and Dipole Moments Ions Electron Configurations and Sizes Predicting Formulas of Ionic Compounds Sizes of Ions... 

In biology, the total concentration of ions in solution is very important in metabolic and cellular processes. When an ionic compound dissolves, the relative concentrations of the ions in the solution depend on the chemical formula of the compound. For example, a 1.0 Msolution of NaCl is 1.0 M in Na ions and 1.0 Min Cl ions, and a 1.0 M solution of Na2S04 is 2.0 M in Na ions and 1.0 M in SO/ ions. Thus, the concentration of an electrolyte solution can be specified either in terms of the compound used to make the solution (1.0 M Na2S04) or in terms of the ions in the solution (2.0 M Na and 1.0MS04 ). 

These chapters introduce you to the two main types of bonding found in nature ionic bonding and cov ent bonding. 1 show you how to predict the formulas of ionic compounds (salts) and how to name them. 1 explain covalent bonding, how to draw Lewis structural formulas, and how to predict the shapes of simple molecules. 1 tell you about chemical reactions and show you the various general types. In addition, 1 cover chemical equilibrium, kinetics, and electrochemistry — batteries, cells, and electroplating. 

We can apply this principle in predicting the formulas of ionic compounds. To predict the formula of an ionic compound, we must recognize that chemical compounds are always electrically neutral. In addition, the metal will lose electrons to achieve noble gas configuration and the nonmetal will gain electrons to achieve noble gas configuration. Consider the compound formed between barium and sulfur. Barium has two valence electrons, whereas sulfur has six valence electrons ... 

Formulas of ionic compounds were introduced in Section 6.8. Chemical compounds are electrically neutral. 

Aluminum oxide is an ionic compound. Sketch the transfer of electrons from aluminum atoms to oxygen atoms that accounts for the chemical formula of the compound AljOj. 

Finding out why and how ions are formed Understanding how ions create chemical bonds Deciphering the formulas of ionic compounds Neiming ionic compounds Connecting conductivity and ionic bonds... 

So we can use the Lewis model to predict the correct chemical formulas for ionic compounds. For the compound that forms between K and Cl, for example, the Lewis model predicts a ratio of one potassium cation to every one chloride anion, KCl. In nature, when we examine the compound formed between potassium and chlorine, we indeed find one potassium ion to every chloride ion. As another example, consider the ionic compound formed between sodium and snlfnr. The Lewis symbols for sodinm and sulfur are ... 

Oxidation numbers can be used to determine the chemical formulas for ionic compounds. If the oxidation number of each ion is multiplied by the number of that ion present in a formula unit, and then the results are added, the sum must be zero. 

In Section 3-2, we learned that the formula unit of an ionic compound is the simplest electrically neutral collection of cations and anions from which the chemical formula of the compound can be established. The Lewis structure of sodium chloride (equation 10.1) represents its formula unit. For an ionic compound of a main-group element, (1) the Lewis symbol of the metal ion has no dots if all the valence electrons are lost, and (2) the ionic charges of both cations and anions are shown. These ideas are further illustrated through Example 10-2. 

The chemical formula of an ionic compound shows the ratio of the numbers of atoms of each element present in one formula unit. A formula unit of an ionic compound is a group of ions with the same number of atoms of each element as appears in its formula. 

C02-0069. Write the chemical formulas of all ionic compounds that can form between the elements listed in Problem 2.41. 

By convention, the chemical formulas of many ionic compounds do not explicitly state the charges of the ions. It is not necessary to do so when the species involved form ions with only one possible charge. However, many metals form more than one type of stable cation. For example, copper forms two different oxides, black CuO and red C112 O. The oxide anion has a -2 charge, so for the first compound to be neutral the copper cation must bear a +2 charge. In C112 O, each copper ion must have +1 charge. 

For transition metals, the lanthanides, and the actinides, no such simple rule exists. If we accept the ions charges as chemical facts, we can still write the empirical formulas for ionic compounds so that the net (overall) charge is zero. If we had Fe2+ and O2-, the compound would require a minimum of one of each of the elements for a neutral formula, FeO, whereas Fe3+ and O2- would have the formula Fe2C>3. 

Through the use of chemical symbols and numerical subscripts, the formula of a compound can be written. The simplest formula that may be written is the empirical formula. In this formula, the subscripts are in the form of the simplest whole number ratio of the atoms in a molecule or of the ions in a formula unit. The molecular formula, however, represents the actual number of atoms in a molecule. For example, although CH20 represents the empirical formula of the sugar, glucose, C6H1206, represents the molecular formula. For water, H20, and carbon dioxide, C02, the empirical and the molecular formulas are the same. Ionic compounds are generally written as empirical formulas only for example, common table salt is NaCl. 

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