Oxidation Chemistry

Oxidation is the most important high temperature reaction. Metals or alloys are oxidised when immersed in a strongly oxidising medium such as air or oxygen. Oxidation can also occur in other conditions, such as sulphur dioxide and carbon dioxide, which have comparatively low potential for oxidation. In the simplest form, an oxidation reaction is represented by the interaction of metal with oxygen to form an oxide.

The term oxidation refers to any chemical change in which the number of oxidation increases while the term reduction refers to any change which results in a decrease in the number of oxidations. The idea of oxidation state has been devised in order to keep track of the movement of electrons. In other words, an oxidation state is defined for each atom or in certain cases, a group of atoms in a molecule. Oxidation numbers of a compound is always zero. It is important to remember that we assign oxidation states to atoms only when they aren’t in their elemental forms.

Changes in Oxidation State

Loss of electrons is oxidation. When an atom loses electrons, its oxidation state increases. An example is magnesium metal. If a magnesium atom loses two electrons to form a Mg²⁺ ion, its oxidation state increases from 0 to +2. Hence increase in oxidation state is oxidation. The gain of electrons is reduction. When an atom gains electrons, its oxidation state decreases. An example is a chlorine atom. If a chlorine atom gains an electron to form a Cl^– ion, its oxidation state decreases from 0 to 1. Hence decrease in oxidation state is reduction.

Oxidation and reduction can take place even if no oxygen or hydrogen is involved. One of the most important ways is in an electron transfer reaction, where one substance gives up electrons and another substance takes in electrons. So what is oxidation? Oxidation is nothing but the loss of electrons or loss of hydrogen. Oxidation and reduction takes place even if no oxygen or hydrogen is involved. One of the most important ways is in an electron transfer reaction, where one substance gives up electrons and another substance takes in electrons.

Types of Oxidation state of elements

Positive Oxidation States – When all p-electrons are involved in bonding with more electronegative atoms, +3 oxidation state results. When all the 5 valence electrons are involved in bonding, +5 oxidation state results. The stability of +3 oxidation state increases while that of 5 decreases as we move from top to bottom in the group that is nitrogen to bismuth. This is due to inert pair effect.

Negative Oxidation State – The elements of group 15 have five electrons in their valence shell. Hence, by gaining three more electrons from more metallic elements they form triple charged negative ions and acquire the nearest inert gas configuration  for example nitrides and phosphide ions. So they show -3 oxidation state. On moving down the group the stability of -3 oxidation state decreases.

Oxidation numbers also referred to as oxidation states are numerical numbers of molecules or ions allocated to atoms depending on a set of laws. The oxidation state describes the degree of oxidation of an atom. Though bonds can never be 100 percent ionic, an oxidation state represents the charge that would exist if all bonds on an atom were purely ionic.