what is the difference between oxidation state,charge and valency of an element?

Oxidation means the lose of electrons, while Valency is the number of electrons in valence shell(last shell of an atom) and when electrons are lose or gained by am atom, the atom gets a charge.

In detail...,

Valency is the number of electrons in Valence shell of an atom

Ex. Oxygen has a valency of -2 (as it has 6 electrons in valence shell and need only two electrons to complete Octate.)

Oxidation is the removal of electrons from an atom,

Ex. When Na reacts with Cl, Na Undergoes oxidation to form Na+ ion and chlorine undergoes Reduction to form Cl- ion.

When an atom loses or gains electrons, the atom gets charge.

Ex. In above example, Na looses 1 electron , and therefore, gets a positive charge.

Hope i helped...:)