Apparent charge on atom in a molecule is:

Explanation

The correct answer is Option C: Oxidation number. The oxidation number represents the apparent charge on an atom in a molecule, assuming that the electrons in a bond are assigned to the more electronegative atom. This concept helps in understanding redox reactions and electron transfer. Option A: Valency is incorrect because it describes the number of bonds an atom can form, not its charge. Option B: Coordination number is incorrect as it refers to the number of atoms bonded to a central atom, not an atom's charge. Option D: Charge number is incorrect because it relates to the quantized electric charge of particles, not the effective charge in a molecular context.