Question

\(\mathrm{B} \mathrm{F}_{3}\) adducts with \(\mathrm{NII}_{3}\) because (1) \(\mathrm{N}\) contains the highest electroncgativity. (2) \(\mathrm{N}\) contains the lowest atomic size. (3) \(\mathrm{NII}_{3}\) contains lone pair of clectrons and \(\mathrm{BF}_{3}\) is electron-deficient molccule. (4) Boron contains the lowest atomic size.

Short answer

Option 3: NH\textsubscript{3} contains a lone pair of electrons and BF\textsubscript{3} is an electron-deficient molecule.

Step-by-step solution

Identify Key Characteristics of BF\textsubscript{3}

Recognize that \( \text{BF}_{3} \) is an electron-deficient molecule because boron has only six electrons in its valence shell, making it highly likely to act as a Lewis acid, which seeks electrons.

Identify Key Characteristics of NH\textsubscript{3}

Understand that \( \text{NH}_{3} \) has a lone pair of electrons on the nitrogen atom, which can be donated to an electron-deficient species like \( \text{BF}_{3} \). This makes \( \text{NH}_{3} \) a Lewis base.

Analyze the Given Options

Evaluate each option provided to justify the adduct formation:1. While nitrogen is highly electronegative, this property alone does not explain the adduct formation with \( \text{BF}_{3} \).2. The atomic size of nitrogen being small does not directly contribute to the formation of the adduct.3. The presence of a lone pair on \( \text{NH}_{3} \) and the electron deficiency of \( \text{BF}_{3} \) explains the adduct formation due to electron pair donation.4. The size of boron, being small, is not the primary reason for adduct formation.

Select the Correct Option

Based on the analysis, the correct reason for the adduct formation is option 3: \( \text{NH}_{3} \) contains a lone pair of electrons and \( \text{BF}_{3} \) is an electron-deficient molecule.

Key concepts

Electron Deficiency

Electron deficiency occurs when an atom has fewer electrons in its valence shell than it needs to complete a stable, electron-rich configuration. For example, in the case of \(\text{BF}_3\), boron has only six electrons in its valence shell instead of the octet configuration commonly found in stable molecules. This makes \(\text{BF}_3\) an electron-deficient molecule, causing it to seek out additional electrons from other sources to achieve stability.
Electron-deficient molecules are highly reactive and usually act as Lewis acids. They can accept electrons from molecules that have extra electron pairs to donate. Understanding this concept is crucial in predicting the behavior of such molecules in chemical reactions and their tendency to form adducts with Lewis bases.

Lone Pair Donation

Lone pair donation refers to the ability of a molecule with one or more pairs of non-bonding electrons to donate these electrons to another molecule. In the context of \(\text{NH}_3\), nitrogen has a lone pair of electrons that it can offer for bonding. This makes \(\text{NH}_3\) a good candidate as a Lewis base.
When \(\text{NH}_3\) meets an electron-deficient molecule like \(\text{BF}_3\), it can donate its lone pair to boron, which is seeking additional electrons. This donation forms a Lewis acid-base adduct, where the two molecules are connected through the shared electrons.
Understanding lone pair donation is important because it explains why certain reactions occur and helps us predict the formation of new compounds.

Lewis Acid

A Lewis acid is a compound that can accept a pair of electrons from a Lewis base to form a coordinate covalent bond. In our example, \(\text{BF}_3\) acts as a Lewis acid. Boron in \(\text{BF}_3\) is electron-deficient and seeks additional electrons to attain a more stable configuration.
Key characteristics of Lewis acids include:

• Electron deficiency
• High reactivity
• Ability to accept lone pairs of electrons

Lewis acids play a crucial role in various chemical reactions, especially in forming adducts with Lewis bases. This property is widely used in synthetic chemistry to create complex molecules by combining simpler ones.

Lewis Base

A Lewis base is a molecule or ion that can donate a pair of electrons to a Lewis acid. \(\text{NH}_3\) serves as an excellent example of a Lewis base. Nitrogen, with its lone pair of electrons, has the capability to share these electrons with electron-deficient species like \(\text{BF}_3\).
Key characteristics of Lewis bases include:

• Presence of lone pairs of electrons
• High electron density
• Ability to donate electrons

Lewis bases are fundamental in forming Lewis acid-base adducts, which are essential for many chemical reactions. The interaction between Lewis acids and Lewis bases is at the heart of understanding how molecules combine and react.