Definition I
Oxidation is a process which involves the loss of one or more electron by an atom iron or molecule
Example
$2 Na+ Cl_2 -> 2NaCl$
$2Na -> 2Na^+ + 2e^-$
Definition II
Oxidation is addition of oxygen/electronegative element to a substance or removal of hydrogen/electropositive element from a substance
Example
$2 Mg (s) + O_2 (g) -> 2 MgO (s)$
What is reduction
Reduction can be defined as
Definition I
Reduction is a process which involves the gain of one or more electron in an atom, Iron, molecule
Example
$2 Na+ Cl_2 -> 2NaCl$
$Cl_2 + 2e^- -> 2Cl^-$
Definition II
Reduction is removal of oxygen/electronegative element from a substance or addition of hydrogen/electropositive element to a substance
Example
$2 HgO (s) -> 2 Hg (l) + O_2 (g)$
What is Oxidizing agent
It is a substance which can accept one or more electrons from the substances has all two species atom, Iron, molecule which undergo reduction are in fact oxidants or oxidizing agents
What is Reducing agents
Tt is a substance which can readily lose or one or more electrons to other substances does all the species atom and molecule which undergo oxidation are in fact reductant or reducing agents
Redox Reaction
Oxidation-reduction reactions are complementary reactions. Whenever any substance is oxidised, another substance is always reduced at the same time and vice versa. In other words, the oxidation reduction. reactions always occur simultaneously i.e., they always go hand in hand or side by side. Example
$2HgCl_2 (aq) + SnCl_2 (aq) -> Hg_2Cl_2 (s)+SnCl_4 (aq)$
Here stannous chloride is oxidized to stannic chloride because of the addition of electronegative element chlorine to it.
At the same time $HgCl_2$ is reduced to $Hg_2Cl_2$ because of the addition of mercury to mercuric chloride.
Therefore $SnCl_2$, is oxidised by $HgCl_2$, and $Hg_2Cl_2$, is reduced by $SnCl_2$. Hence, $HgCl_2$, acts as an oxidising agent and $SnCl_2$, acts as a reducing agent in this reaction.
