Question

how loss and gain of ekectrons are related to oxidation and reduction

Answer 1

The process in which a substanceloses an electron in a chemical reaction is called oxidation. ... The atoms that lost electrons are said to be oxidized. Atoms can be oxidized by nonmetals. Reduction is gain of electrons and thus gaining of negative charge.

Answer 2

The original view of oxidation and reduction is that of adding or removing oxygen. An alternative view is to describe oxidation as the losing of electrons and reduction as the gaining of electrons. One example in which this approach is of value is in the high temperature reaction of lead dioxide .

2PbO2 -> 2PbO + O2

In this reaction the lead atoms gain an electron (reduction) while the oxygen loses electrons (oxidation).

This electron view of oxidation and reduction helps you deal with the fact that "oxidation" can occur even when there is no oxygen! The definition of redox reactions is extended to include other reactions with nonmetals such as chlorine and bromine. For example, the reaction

Mg + Cl2 -> Mg2+ + 2Cl-

Magnesium loses electrons and is therefore said to be "oxidized", whereas the chlorines gain electrons and are said to be reduced. Another way to judge that the chlorine has been reduced is the fact that the charge on the atoms is made more negative, or reduced.