Oxidation numbers prediction

I The oxidation numbers predicted by Figure 16.2 will not be correct for aU elements in all compounds. 

The metals in the following compounds can have various oxidation numbers. Predict the charge on each metal ion, and write the name for each compound. 

Strategy The structure can be obtained by removing an oxygen atom from H O, (Figure 21.8). Relative acid strengths can be predicted on the basis of the electronegativity and oxidation number of the central nonmetal atom, following the rules cited above. 

Oxidation-reduction reactions must be balanced if correct predictions are to be made. Just as in selecting a route for a trip from San Francisco to New York, there are several ways to reach the desired goal. Which route is best depends to some extent upon the likes and dislikes of the traveler. We will discuss two ways to balance oxidation-reduction reactions—first, using half-reactions and, next, using the oxidation numbers we have just introduced. 

Si044, and deduce the formal charges and oxidation numbers of the atoms. Use the VSEPR model to predict the shape of the ion. 

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. 

A nonmetal may adopt any oxidation number between the values predicted in the preceding two paragraphs. The only exceptions are fluorine, which is only -1 in compounds, and helium, neon, and argon, which have no known compounds. When there is a choice of oxidation states, there must be additional information available in order to allow you to choose the correct state. 

When the itinerant state is formed, a volume collapse AV/V is always encountered, as predicted by the theory of the preceding sections. In one of the lanthanides, cerium, this volume collapse is particularly accentuated for its isostructural transition from the y to the a form, possibly associated with a change in metallic valence from three to four (both oxidation numbers are stable in cerium chemistry) (see Fig. 1 of Chap. A),... 

Oxidation numbers, sometimes called oxidation states, are signed numbers assigned to atoms in molecules and ions. They allow us to keep track of the electrons associated with each atom. Oxidation numbers are frequently used to write chemical formulas, to help us predict properties of compounds, and to help balance equations in which electrons are transferred. Knowledge of the oxidation state of an atom gives us an idea about its positive or negative character. In themselves, oxidation numbers have no physical meaning they are used to simplify tasks that are more difficult to accomplish without them. 

In order to examine the workings of oxidation and reduction, the first order of business is to determine the oxidation number. The oxidation number is essentially what we have called charge so far. Up to now we have simply looked up the charge in a table, but now we have a slightly different set of rules for determining the oxidation number, as there is some variation not predicted by tables. 

One of the main purposes for using oxidation numbers is to follow the movement of electrons during an oxidation-reduction reaction. Doing so helps to predict the products and determine the outcomes of such reactions. There are a few different ways to analyze redox reactions, but we will focus on only one the ion-electron method (also called the half-reaction method). The procedure requires that you know the reactants and products of the reaction, but, by going through the process, you will gain a better understanding of the mechanisms by which these reactions proceed. 

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. 

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. 

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. 

Every element has an oxidation number of zero when it is uncombined (rule 2, Section 16.1). This second simple rule allows us to predict about 100 more oxidation numbers. (Some compounds have atoms with oxidation numbers of zero. For example, the carbon atom in formaldehyde CH2O has an oxidation number of zero.)... 

If oxidation number and coordination number increase simultaneously, the expected frequency shifts cannot be predicted with confidence, since both properties lead to opposing frequency changes. The influence of the increased oxidation number generally dominates ... 

Since so much can be predicted or at least rationalized on the basis of the periodicity of a few simple atomic properties, especially Pauling electronegativity, size, and charge (or oxidation number) see Oxidation Number) of the atoms or ions involved, we begin by looking at these trends in some detail (beyond that done in General Chemistry courses) and... 

A simple model predicts that the ease of removal of a fluoride ion from a xenon fluoride molecule should decrease in the order XeF > Xe 4 > Xep6, as the oxidation number and positive charge on the xenon atom rise. That the actual sequence is XeFe > Xep2 > Xep4, was first indicated by comparative Studies of reactions of the fluorides with acceptors, and was later confirmed by enthalpy measurements for the processes ... 

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