Oxidation numbers from formulas

In most cases, assigning oxidation numbers from formulas by drawing electron dot diagrams is more time-consuming than necessary. The following set of rules speeds the assignment of oxidation numbers for the elements in most cases. If these rules do not work for assigning oxidation numbers in a particular case, the electron dot method may be used. 

In Sec. 13.2 we will learn to determine oxidation numbers from the formulas of compounds and ions. We will learn how to assign oxidation numbers from electron dot diagrams and more quickly from a short set of rules. We use these oxidation numbers for naming the compounds or ions (Chap. 6 and Sec. 13.4) and to balance equations for oxidation-reduction reactions (Sec. 13.5). In Sec. 13.3 we will learn to predict oxidation numbers for the elements from their positions in the periodic table in order to be able to predict formulas for their compounds and ions. 

Section 16.1 introduces the concept of oxidation number and how to calculate the oxidation number of an element from the formula of the compound or ion of which it is a part. Section 16.2 describes how to use the oxidation numbers to name compounds, formalizing and extending the rules given in Chapter 6. Section 16.3 shows how to predict possible oxidation numbers from the position of the element in the periodic table and how to use these oxidation numbers to write probable formulas for covalent compounds. Section 16.4 presents a systematic method for balancing equations in which oxidation numbers change. 

You will often encounter compounds that contain polyatomic ions, and you will simply look up the symbols and oxidation numbers from the second group of oxidation numbers. For example, let s write the proper chemical formula for the compound called calcium carbonate. Use Figures 5-2a and 5-2b to find the symbols and oxidation numbers associated with each ion. 

The other procedure which is of value in the calculation of the equivalents of substances is the oxidation number method. This is a development of the view that oxidation and reduction are attended by changes in electronic charge and was originally developed from an examination of the formulae of the initial and final compounds in a reaction. The oxidation number (this will be abbreviated to O.N.) of an element is a number which, applied to that element in a particular compound, indicates the amount of oxidation or reduction which is required to convert one atom of the element from the free state to that in the compound. If oxidation is necessary to effect the change, the oxidation number is positive, and if reduction is necessary, the oxidation number is negative. 

With these rules, we can quickly and easily calculate the oxidation numbers of an element most of the time from the formulas of its compounds. 

If phosphorus pentoxide were POs, phosphorus would have an oxidation number of + 10, which exceeds its group number. The maximum oxidation number that phosphorus can have is + 5 (from group VA), and so the formula is P205. (The compound cannot be a peroxide it was named oxide. )... 

An isolated cs plane or a random array of cs planes, known as the Wadsley defect, still gives rise to nonstoichiometry. Regularly recurring cs planes result in a homologous series of stoichiometric intermediate phases. Occurrence of such equidistant cs planes in a crystal indicates a cooperative mechanism. The formula of a cs phase depends on the cs plane index as well as the width of the parent slab between cs planes. If MO is the formula of the parent line phase, the formula of the homologous series of oxides resulting from cs may be represented as where n is the width (number of... 

Can you calculate the oxidation number of carbon solely from the molecular formula of ethanol (C2H60) Explain. How does the oxidation number calculated from the molecular formula compare to the values obtained in Table 2.5 ... 

Silver differs markedly from copper in forming few 0x3 compounds. One of these is silver oxynitratc or silvcrdl, III) nitrate which has the empirical formula AgO 145(1 03)3453, in which the average oxidation number of silver is 2.448, It is prepared by action of fluorine upon aqueous silver nitrate or is obtained as an anodic deposit by electrolysis of silver nitrate in dilute HNO3. 

The sum of all the oxidation numbers in a formula must equal zero. By using the oxidation numbers that you know from the oxidation number rules, combined with the idea of a zero total you can calculate the oxidation number of an element that does not fit the rules. 

From these examples the rules of nomenclature are apparent. The central atom (like Fe, Cu, Co, Ag) is followed by the formula of the ligand (CN, NH3, H20, S203), with the stoichiometric index number, (which, in the case of monodentate ligands is equal to the coordination number). The formula is placed inside square brackets, and the charge of the ion is shown outside the brackets in the usual way. When expressing concentrations of complexes, brackets of the type will be used to avoid confusion. In the name of the ion, first the (Greek) number, then the name of the ligand is expressed, followed by the name of the central atom and its oxidation number (valency). 

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. 

We do not really need oxidation numbers when working with compounds of monatomic ions we can use the charges to write formulas, and we can predict the charges from the periodic table or deduce them from the formulas. When working with compounds with covalent bonds and polyatomic ions (which also... 

In Section 16.1, we learned how to determine oxidation numbers of atoms of elements from the formulas of their ions or molecules. This section shows the opposite—how to write formulas for compounds based on knowledge of the possible oxidation numbers of the atoms of the elements. Predicting possible oxidation numbers is straightforward, but learning which are the most important oxidation numbers of even some of the most familiar elements takes a good deal of experience. 

Oxidation numbers (also called oxidation states) are used as a sort of bookkeeping method for keeping track of the electrons in polyatomic ions or compounds that have covalent bonds. (For monatomic ions, the charge on the ions works just as well.) Oxidation number is defined as the number of electrons in a free atom minus the number controlled by that atom in the compound. The control of electrons in a covalent bond is assigned to the more electronegative atom of the bond. Eight simple rules can be used to determine the oxidation number of an element from the formula of its compound or ion (Section 16.1). 

Oxidation numbers are used in the Stock system for naming compounds. Positive oxidation numbers are denoted as Roman numerals in parentheses in the names of the compounds the numbers of atoms or ions can be deduced from the oxidation numbers. (In contrast, the subscripts in formulas give the numbers of atoms or ions, from which the oxidation numbers may be deduced.) (Section 16.2). 

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