Understanding Oxidation States in Halogen Oxides

Oxidation state, also known as oxidation number, is a hypothetical charge an atom would have if all bonds to atoms of different elements were 100% ionic. To determine the oxidation state of the halogen in these oxides, we use the common oxidation state of oxygen, which is typically -2, except in peroxides or superoxides (which these are not). The sum of the oxidation states of all atoms in a neutral compound is zero.

Calculating Halogen Oxidation States

Let's calculate the oxidation state for the halogen in each given oxide:

• A) ClO₂: The compound is neutral, so the sum of oxidation states is zero. Let $x$ be the oxidation state of Cl.

  \begin{equation*} x + 2 \times (-2) = 0 \end{equation*}

  \begin{equation*} x - 4 = 0 \end{equation*}

  \begin{equation*} x = +4 \end{equation*}

  The oxidation state of Cl in ClO₂ is +4.
• B) Cl₂O₃: The compound is neutral. Let $x$ be the oxidation state of Cl.

  \begin{equation*} 2x + 3 \times (-2) = 0 \end{equation*}

  \begin{equation*} 2x - 6 = 0 \end{equation*}

  \begin{equation*} 2x = 6 \end{equation*}

  \begin{equation*} x = +3 \end{equation*}

  The oxidation state of Cl in Cl₂O₃ is +3.
• C) BrO₂: The compound is neutral. Let $x$ be the oxidation state of Br.

  \begin{equation*} x + 2 \times (-2) = 0 \end{equation*}

  \begin{equation*} x - 4 = 0 \end{equation*}

  \begin{equation*} x = +4 \end{equation*}

  The oxidation state of Br in BrO₂ is +4.
• D) I₂O₄: The compound is neutral. Let $x$ be the oxidation state of I.

  \begin{equation*} 2x + 4 \times (-2) = 0 \end{equation*}

  \begin{equation*} 2x - 8 = 0 \end{equation*}

  \begin{equation*} 2x = 8 \end{equation*}

  \begin{equation*} x = +4 \end{equation*}

  The oxidation state of I in I₂O₄ is +4.
• E) I₂O₅: The compound is neutral. Let $x$ be the oxidation state of I.

  \begin{equation*} 2x + 5 \times (-2) = 0 \end{equation*}

  \begin{equation*} 2x - 10 = 0 \end{equation*}

  \begin{equation*} 2x = 10 \end{equation*}

  \begin{equation*} x = +5 \end{equation*}

  The oxidation state of I in I₂O₅ is +5.

Here is a summary of the oxidation states:

Comparing Oxidation States for Halogen Oxides

The question asks which pair of these halogen oxides has oxidation states for the halogens that are not the same (i.e., are different). Let's look at the options provided:

• Option 1: (A) ClO₂ and (E) I₂O₅

  Oxidation state of Cl in ClO₂ is +4.

  Oxidation state of I in I₂O₅ is +5.

  The oxidation states (+4 and +5) are different.

• Option 2: (B) Cl₂O₃ and (E) I₂O₅

  Oxidation state of Cl in Cl₂O₃ is +3.

  Oxidation state of I in I₂O₅ is +5.

  The oxidation states (+3 and +5) are different.

• Option 3: (C) BrO₂ and (D) I₂O₄

  Oxidation state of Br in BrO₂ is +4.

  Oxidation state of I in I₂O₄ is +4.

  The oxidation states (+4 and +4) are the same.

• Option 4: (D) I₂O₄ and (E) I₂O₅

  Oxidation state of I in I₂O₄ is +4.

  Oxidation state of I in I₂O₅ is +5.

  The oxidation states (+4 and +5) are different.

Based on the calculations, the pair Cl₂O₃ and I₂O₅ has halogen oxidation states of +3 and +5, respectively. These oxidation states are not the same.

Revision Table: Halogen Oxides and Oxidation States

Additional Information about Halogen Oxidation States

Halogens (Fluorine, Chlorine, Bromine, Iodine, Astatine) are in Group 17 of the periodic table. While Fluorine almost always has an oxidation state of -1 in its compounds, other halogens can exhibit a variety of positive oxidation states when bonded to more electronegative elements like oxygen.

Common positive oxidation states for Cl, Br, and I in oxides and oxyacids include +1, +3, +4, +5, and +7. Examples:

• +1: Cl₂O, HOCl (hypochlorous acid)
• +3: Cl₂O₃, HClO₂ (chlorous acid)
• +4: ClO₂, BrO₂, I₂O₄
• +5: ClO₃^-, I₂O₅, HIO₃ (iodic acid)
• +7: Cl₂O₇, HClO₄ (perchloric acid), HIO₄ (periodic acid)

The specific oxidation state depends on the number of oxygen atoms bonded and the overall charge of the species (if it's an ion).