The oxidation number of oxygen in H2 O2 (A) -1 (B) -2 (C) -3 (D) -1/2

By BYJU'S Exam Prep

Updated on: September 25th, 2023

The oxidation number of oxygen in H2 O2 is -1. The number of charges (positive or negative) assigned to an atom in a molecule or ion in accordance with a set of arbitrary principles determines the oxidation number/oxidation state of that element in a compound.

Rules for Assigning Oxidation Number 

  • All elements have a zero oxidation number when they are in their free state.
  • Fluorine, which has the highest electronegative charge, has an oxidation number of -1 in all compounds.
  • Monoatomic ions have an oxidation number equal to their charge. For instance:
  • Li+, Ca2+, and Al3+ have oxidation states of +1, +2, and +3, respectively.
  • Cl- and SO42- have oxidation states of 1 and 2, respectively.
  • All compounds, with the exception of ionic hydrides, have hydrogen in the +1 oxidation state (-1 oxidation state).
  • Except for peroxides, which have an oxidation state of 1, oxygen is in a compound in a -2 state.
  • Alkaline earth metals (Be, Mg, etc.) have +2 oxidation states, while alkali metals (Li, Na, K, etc.) always have a +1 oxidation state.
  • The charge of the ligands is considered in transition metal complexes.
  • The ligands can be divided into neutral, cationic, and anionic types. The neutral ligands are charge-free.
  • Hydrogen peroxide, or H2O2.
  • Peroxides are substances in which two oxygens are linked together by the bond O-O.
  • There are two hydrogen atoms in the molecule hydrogen peroxide, meaning that its two negative charges are balanced by its two positive hydrogen ion charges.
  • Therefore, the combined charge of two oxygen atoms is negative.
  • In that regard, we might argue that each oxygen bears a charge = -2/2 = -1 because the molecule is neutral overall.


The oxidation number of oxygen in H2 O2, (A) -1 (B) -2 (C) -3 (D) -1/2

The oxidation number of oxygen in H2 O2 is -1. The oxidation number can be found by knowing the number of charges which are assigned to an atom.

Our Apps Playstore
SSC and Bank
Other Exams
GradeStack Learning Pvt. Ltd.Windsor IT Park, Tower - A, 2nd Floor, Sector 125, Noida, Uttar Pradesh 201303
Home Practice Test Series Premium