Define atomic radius. Explain the factors affecting it and its periodicity.

Hint: Here we have to firstly state what does the atomic radius mean. Now after that we get the nature and the impact of the radius. Now after that we can enlist the factors like effective nuclear charge and the number of shells. They are the ones which govern the size of the radius.

Complete step by step answer:
For the case of oxidising agents.
Whenever in any reaction, $H_2O_2$ acts as an oxidizing agent, there would be a change in the evident oxidising state of the oxygen atom of the compound. In the change, the oxidation state of the oxygen of hydrogen peroxide will get reduced from -1 to -2 .
Atomic radius is the radius of an atom . Atomic radius is defined as the distance from the center of the nucleus to the outermost shell containing the electron , It measures the size of an atom . If the atom is a metal , atomic radius states the metallic radius while if atom is a non - metal , atomic radius states the covalent radius .
Factors affecting atomic Radius :
Effective nuclear charge : The net charge of the nucleus experienced by the outermost electron is known as effective nuclear charge : It is represented by Z. With increase in Z,effective atomic radius decreases .
Number of shells : with increase in number of shells or principal quantum number , atomic radius increases .

Note:
Depending on the definition, the term may apply only to isolated atoms, or also to atoms in condensed matter, covalently bonding in molecules, or in ionized and excited states; and its value may be obtained through experimental measurements, or computed from theoretical models.