Oxidation Numbers Keeping Track of Electrons

K.2 Oxidation Numbers Keeping Track of Electrons F94 Toolbox K.l How to assign oxidation numbers F95... 

SECTION 4.4 Oxidation is the loss of electrons by a substance, whereas reduction is the gain of electrons by a substance. Oxidation numbers keep track of electrons during chemical reactions and are assigned to atoms using specific rules. The oxidation of an element results in an increase in its oxidation number, whereas reduction is accompanied by a decrease in oxidation number. Oxidation is always accompanied by reduction, giving oxidation-reduction, or redox, reactions. 

Chemists have found a way to keep track of electrons by assigning an oxidation number to each element. The oxidation number is defined so that... 

Oxidation numbers are just a bookkeeping method used to keep track of electron transfers. In a covalent molecule or a polyatomic ion, the oxidation number of each element does not represent an ionic charge, because the elements are not present as ions. However, to assign oxidation numbers to the elements in a covalent molecule or polyatomic ion, you can pretendthe bonds are ionic. 

How can you tell when a redox reaction is taking place The answer is that we assign to each atom in a substance a value called an oxidation number (or oxidation state), which indicates whether the atom is neutral, electron-rich, or electron-poor. By comparing the oxidation number of an atom before and after reaction, we can tell whether the atom has gained or lost electrons. Note that oxidation numbers don t necessarily imply ionic charges. They are simply a convenient device to help keep track of electrons in redox reactions. 

In order to keep track of electron shifts in oxidation-reduction reactions, it is convenient to use the concept of oxidation number or oxidation state of various atoms involved in oxidation-reduction reactions. The oxidation number is defined as the formal charge which an atom appears to have when electrons are counted in accordance with the following rather arbitrary rules. 

The concept of oxidation states (also called oxidation numbers) provides a way to keep track of electrons in oxidation-reduction reactions. Oxidation states are defined by a set of rules, most of which describe how to divide up the shared electrons in compounds containing covalent bonds. However, before we discuss these rules, we need to discuss the distribution of electrons in a bond. 

By tracking oxidation numbers, you can tell whether an atom is oxidized or reduced. If the oxidation number of an atom increases during a reaction, the atom is oxidized. If the oxidation number decreases, the atom is reduced. Like other models, oxidation numbers have limits. You should consider them a bookkeeping tool to help keep track of electrons. In some cases, additional rules are needed to find values that make sense. 

Oxidation numbers are assigned to elements to name inorganic compounds, to keep track of electrons in electron transfer (oxidation-reduction) reactions, and to explore trends in chemical reactivity across the periodic table. 

The many reactions that involve the transfer of electrons from one species to another are called oxidation-reduction reactions, or simply, redox reactions. We use oxidation numbers to keep track of electron transfers. The systematic naming of compounds (Sections 4-11 and 4-12) also makes use of oxidation numbers. 

To keep track of electrons in redox reactions, it is useful to assign oxidation numbers to the reactants and products. An atom s oxidation number, also called oxidation state, signifies the number of charges the atom would have in a molecule (or an ionic compound) if electrons were transferred completely. For example, we can rewrite the above equations for the formation of HCl and SO2 as follows ... 

The concept of oxidation states (sometimes called oxidation numbers) lets us keep track of electrons in oxidation-reduction reactions by assigning charges to the various atoms in a compound. Sometimes these charges are quite apparent. For example, in a binary ionic compound the ions have easily identified charges in sodium chloride, sodium is +1 and chlorine is -1 in magnesium oxide, magnesium is +2 and oxygen is -2 and so on. 

The concept of oxidation numbers was developed as a simple way of keeping track of electrons in a reaction. Using oxidation numbers, you can determine whether or not electrons have been transferred from one atom to another. If electrons have been transferred, an oxidation-reduction reaction has occurred. 

The manganese-oxygen bonds in the manganate(vii) ion are polar covalent bonds. The assignment of electrons between atoms in calculating an oxidation state is purely a set of useful but artificial beliefs for the understanding of many chemical reactions. Oxidation numbers are not real - they are simply useful mathematical constructs used to keep track of electrons during redox reactions. 

The oxidation number, or oxidation state, is a bookkeeping device used to keep track of the number of electrons formally associated with a particular element. The oxidation number is meant to tell how many electrons have been lost or gained by a neutral atom when it forms a compound. Because oxidation numbers have no real physical meaning, they are somewhat arbitrary, and not all chemists will assign the same oxidation number to a given element in an unusual compound. However, there are some ground rules that provide a useful start. 

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. 

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, sometimes called oxidation states, help chemists keep track of the numbers of electrons that surround each atom in a chemical reaction, and how they change in oxidation-reduction reactions. When an atom gains an electron (is reduced), its oxidation number is increased by one. There are some simple rules for assigning oxidation numbers to elements in chemical compounds. These mles are ... 

Oxidation numbers are tools that scientists use in written chemical equations to help them keep track of the movement of electrons in a redox reaction. Like some of the other tools you have learned about in chemistry, oxidation numbers have a specific notation. Oxidation numbers are written with the positive or negative sign before the number (+3, +2), whereas ionic charge is written with the sign after the number (3 +, 2+). 

---