Question

Two \(p\)-block elements \(X\) and \(Y\) form fluorides of the type \(EF_3\). The fluoride compound \(XF_3\) is a Lewis acid and \(YF_3\) is a Lewis base. The hybridizations of the central atoms of \(XF_3\) and \(YF_3\) respectively are

• A. Both \(sp^2\)
• B. Both \(sp^3\)
• C. \(sp^2\) and \(sp^3\)
• D. \(sp^3\) and \(sp^2\)

Hint:

Lewis acidic fluorides generally have electron-deficient central atoms, while Lewis basic fluorides contain lone pairs.

Answer 1

The Correct Option is C

To solve this question, we must identify the \( p \)-block elements \( X \) and \( Y \) that form fluorides of the type \( EF_3 \), and understand the difference in their hybridization based on their Lewis acid or base behavior.

1. First, understand the nature of \( XF_3 \) which acts as a Lewis acid. A Lewis acid has an empty orbital to accept electrons. In \( p \)-block elements, this behavior is typically seen in elements like Boron. For example, \( \text{BF}_3 \) is a well-known Lewis acid because Boron has an empty \( p \)-orbital.
2. The hybridization of Boron in \( \text{BF}_3 \) is \(sp^2\) because it forms three bonds with fluorine and has no lone pairs, leading to a trigonal planar geometry.
3. Now, consider \( YF_3 \) as a Lewis base. A Lewis base has lone pairs of electrons to donate. In the context of the \( p \)-block, a typical example would be Nitrogen, which forms \( \text{NF}_3 \). Nitrogen in \( \text{NF}_3 \) has a lone pair of electrons.
4. The hybridization here is \(sp^3\), since Nitrogen forms three bonds with Fluorine and has one lone pair, resulting in a tetrahedral electron geometry.
5. Therefore, the hybridizations of the central atoms in \( XF_3 \) and \( YF_3 \) are \(sp^2\) and \(sp^3\), respectively.

Based on the analysis above, the correct answer is: \(sp^2\) and \(sp^3\).

The hybridizations are determined by the number of bonds, lone pairs, and the resulting electron pair geometry of the molecular structures:

• Lewis Acid (like Boron): Needs empty orbitals, thus giving rise to an \(sp^2\) hybridization due to three bonds and no lone pairs.
• Lewis Base (like Nitrogen): Possesses lone pairs, hence \(sp^3\) hybridization with three bonds and one lone pair.