Writing, formulas for ionic

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). 

In Chapter 5, we learned to write formulas for ionic compounds from the charges on the ions and to recognize the ions from the formulas of the compounds. For example, we know that aluminum chloride is AICI3 and that VCI2 contains ions. We cannot make comparable deductions for covalent compounds because they have no ions there are no charges to balance. To make similar predictions for species with covalent bonds, we need to use the concept of oxidation number, also called oxidation state. A system with some arbitrary rules allows us to predict formulas for covalent compounds from the positions of the elements in the periodic table and also to balance equations for complicated oxidation-reduction reactions. 

You will name and write formulas for ionic compounds. 

For more practice with writing formulas for ionic compounds, go to Supplemental Practice Problems in Appendix A. 

Formulas are part of the language that is used to communicate information about substances. As a first step in studying this new language, you will learn how to name and write formulas for ionic compounds. 

Writing formulas for ionic compounds that include polyatomic ions is done in the same way formulas are written for binary compounds. The polyatomic ions are treated as single units that bear a charge. The goal is to get the right ratio of cation to anion so that an overall electrically neutral combination is obtained. The same rules used for binary compounds apply here, with one modification ... 

The following examples illustrate how to name ionic componnds and write formulas for ionic componnds based on the information given in Fignre 2.10 and Tables 2.2 and 2.3. 

Answer We use the electroneudality as our guide in writing formulas for ionic compounds. According to Figure 9.1, the Lewis dot symbols of A1 and O 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. 

Formulas for binary ionic compounds In the chemical formula for any ionic compound, the symbol of the cation is always written first, followed by the symbol of the anion. Subscripts, which are small numbers to the lower right of a symbol, represent the number of ions of each element in an ionic compound. If no subscript is written, it is assumed to be one. You can use oxidation numbers to write formulas for ionic compounds. Recall that ionic compounds have no charge. If you add the oxidation number of each ion multiplied by the number of these ions in a formula unit, the total must be zero. 

Write formulas for ionic compounds composed of the following ions. 

Strategy Our guide for writing formulas for ionic compounds is electrical neutrality that is, the total charge on the cation(s) must be equal to the total charge on the anion(s). Because the eharges on the Mg and ions are not equal, we know the formula cannot be MgN. Instead, we write the formula as Mg Ny, where x and y are subscripts to be determined. 

Using the Stock system, the ferrous ion and the ferric ion are iron(II) and iron(III), respectively, so ferrous chloride becomes iron(II) chloride and ferric chloride is called iron(III) chloride. In keeping with modem practice, we will use the Stock system of naming compounds in this textbook. Examples 0.3 and 0.4 illustrate how to name and write formulas for ionic compounds based on the information given in Table 0.3. 

Naming ionic compounds in chemistry is fairly simple when you remember to name the cation (+) first, followed by the anion (-). Writing formulas for ionic compounds is easy if you remember to keep the charges balanced. Then they almost name themselves. 

Write formulas for ionic compounds that would form between the following simple ions. Note that the metal forms two different simple ions, and name each compound two ways. 

Writing Formulas for Ionic Compounds Write a formula for the ionic compound that forms from aluminum and oxygen. Write a formula for the ionic compoimd that forms from magnesium and oxygen. 

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