chapter 7.  ELEMENTS OF GROUPS 16, 17 AND 18 class 12 chemistry textbook solution

3. Answer the following.

vii. Fluorine shows only -1 oxidation state while other halogens show -1, +1, +3, +5 and +7 oxidation states. Explain.


Fluorine (F) exhibits a unique behavior among the halogens when it comes to oxidation states. It primarily shows an oxidation state of -1 in most of its compounds, while other halogens (chlorine, bromine, iodine, and astatine) can display a range of oxidation states, including -1, +1, +3, +5, and +7. This difference in behavior can be explained by several factors:

  1. Electronegativity: Fluorine is the most electronegative element in the periodic table. Electronegativity is a measure of an element’s ability to attract electrons in a chemical bond. Fluorine’s extremely high electronegativity means that it strongly attracts electrons, making it difficult for other elements to pull electrons away from fluorine in a chemical compound. As a result, fluorine tends to acquire a full outer electron shell by gaining one electron to achieve a stable noble gas configuration, resulting in an oxidation state of -1.

  2. Small Atomic Size: Fluorine is the smallest halogen atom in terms of atomic size. Its small size means that it has a high electron density, and its outermost electrons are close to the nucleus. This high electron density contributes to its strong electronegativity and its preference for acquiring an extra electron.

  3. Lack of D Orbitals: Fluorine does not have any available d orbitals in its valence shell, unlike the larger halogens (chlorine, bromine, iodine) which have d orbitals available in higher energy levels. D orbitals can participate in expanded valence shell configurations, allowing these larger halogens to exhibit a wider range of oxidation states. In contrast, fluorine lacks d orbitals to expand its valence shell, limiting it to a -1 oxidation state.

  4. Bond Energy: Fluorine forms very strong and stable bonds with other elements, particularly because of its high electronegativity. This makes it difficult for fluorine to lose electrons and assume positive oxidation states.

In summary, the unique properties of fluorine, including its extreme electronegativity, small atomic size, and lack of available d orbitals, make it highly inclined to acquire electrons and exhibit an oxidation state of -1. On the other hand, the larger halogens have more flexibility in their electron configurations due to the presence of d orbitals, allowing them to display a range of oxidation states beyond -1, including +1, +3, +5, and +7, depending on the specific compounds and reaction conditions.

chapter 7.  ELEMENTS OF GROUPS 16, 17 AND 18 Textbook Solution page 164