Apparent charge on an atom of an element in a molecule or ion is called oxidation number. It may be:

Explanation

Option D is correct.Oxidation number is the apparent charge on an atom of an element in a molecule or ion. It may be positive, negative, or zero.Positive oxidation numbers are assigned to atoms that have lost electrons. For example, in the molecule of sodium chloride (NaCl), the oxidation number of sodium is +1 and the oxidation number of chlorine is -1. This is because sodium has lost an electron to chlorine, and chlorine has gained an electron from sodium. Zero oxidation numbers are assigned to atoms that have neither lost nor gained electrons.For example oxidation numbers are not always the same as the actual charge on an atom. For example, in the molecule of water (H2O), the oxidation number of oxygen is -2, but the actual charge on oxygen is 0. This is because the two hydrogen atoms share their electrons equally with the oxygen atom, so the oxygen atom does not have a net charge. Negative oxidation numbers are assigned to atoms that have gained electrons. In the ion of hydroxide (OH-), the oxidation number of oxygen is -2 and the oxidation number of hydrogen is +1. This is because oxygen has gained two electrons from hydrogen, and hydrogen has lost one electron to oxygen.