General Rules For Assigning Oxidation State

• The oxidation State ( OS) of fluorine is always -1 in all its compound, since it has the highest electronegativity of all reactive elements.
• The OS of hydrogen is +1 in all its compound except in metal hydrides. Like NaH, LiH , in these compounds containing elements that are less electronegative than hydrogen. So this compounds contain OS of hydrogen is -1.
• Oxygen has an OS of -2 . Peroxides like H₂O_2, BaO_{2 etc its OS is -1.}
• _{Alkali metals have an oxidation state of +1 ( except alkalide ).}
• _{Halogens other than fluorine have an OS of -1. OS of chlorine in chloromonofluoride ( ClF ) is +1. In Brominemonochloride (BrCl) OS is -1 .}
• _{Alkaline earth metals have an OS of +2.
  The sum of OS in a polyatomic ion is equal to the charge of the ion.Example . The sum of OS for} SO₄^{2-  is -2.}
• ^{The OS of all the atoms in neutral molecule is zero.}
• ^{The OS of the elements in monoatomic ion is equal to the charge on the ion.}
• ^{The OS of free elements is always zero. Eg. The atoms in He and} N_{2  have OS of 0 ( zero ).}
• _{In binary compounds metal atom has positive OS and non-metals has negative OS. Example, KI.  Oxidation state of K is +1. Oxidation of I is -1.}

• _{The convention is that the cation is written first in a formula followed by the anion. Example, NaH   the H is}   H^{-.                Hcl the H is}  H^+.