Question

Which of the following is the stronger base: \(\mathrm{NF}_{3}\) or \(\mathrm{NH}_{3}\) ? (Hint: \(\mathrm{F}\) is more electronegative than \(\mathrm{H}\).)

Short answer

NH₃ is the stronger base than NF₃.

Step-by-step solution

Understand base strength

The strength of a base is determined by its ability to accept protons. A stronger base is more efficient at accepting protons.

Compare Electronegativity

Consider the electronegativity of the atoms bonded to nitrogen. Fluorine (F) is more electronegative than hydrogen (H). This implies that fluorine will pull electron density away from nitrogen more than hydrogen would.

Analyze Nitrogen's electron availability

In \( ext{NF}_3\), due to fluorine's high electronegativity, nitrogen has less available electron density to donate because fluorine attracts electrons strongly. Conversely, in \( ext{NH}_3\), hydrogen is less electronegative, allowing nitrogen to retain more electron density and making it more available to accept protons.

Conclusion on base strength

Since nitrogen in \( ext{NH}_3\) holds more electron density compared to \( ext{NF}_3\), \( ext{NH}_3\) is a stronger base because it can more readily donate its lone pair of electrons to accept protons.

Key concepts

Electronegativity

Electronegativity is a fundamental concept in chemistry that explains the tendency of an atom to attract electrons towards itself. In the context of ammonia (\(\text{NH}_3\)) and nitrogen trifluoride (\(\text{NF}_3\)), this property plays a crucial role in determining their basicity. Fluorine, being the most electronegative element, pulls electrons towards itself more strongly than hydrogen does. As a result, in \(\text{NF}_3\), the fluorine atoms draw electron density away from the nitrogen atom, decreasing the molecule's ability to act as a base. On the other hand, the less electronegative hydrogen in \(\text{NH}_3\) allows nitrogen to retain more of its electron density, enhancing nitrogen’s capability to act as a base. This stark contrast in electronegativity between fluorine and hydrogen ultimately influences their base strength.

Proton Acceptance

The essence of base strength lies in a molecule's ability to accept protons. When evaluating ammonia (\(\text{NH}_3\)) and nitrogen trifluoride (\(\text{NF}_3\)), we focus on how effectively these compounds can accept a proton. Ammonia is a well-known base because its nitrogen atom can easily donate its lone pair of electrons to accept a proton. Therefore, the retained electron density in ammonia makes nitrogen readily available for protonation, strengthening its base characteristics. Conversely, in nitrogen trifluoride, the high electronegativity of fluorine atoms reduces the effectiveness of nitrogen to share its lone pair, hindering its ability to accept protons effectively.

Electron Density

Electron density refers to the concentration of electrons around an atom, which affects its chemical reactivity. In ammonia (\(\text{NH}_3\)), the electron density around nitrogen is relatively high, because hydrogen does not attract electrons as powerfully as fluorine does. This means that nitrogen in ammonia can easily use its lone pair to bond with a proton.
However, in nitrogen trifluoride (\(\text{NF}_3\)), the electron density around the nitrogen atom is significantly lower due to the presence of electronegative fluorine atoms. These fluorine atoms draw away the electron cloud, making it tougher for nitrogen in \(\text{NF}_3\) to donate its lone pair and act as a base. Therefore, higher electron density around nitrogen in \(\text{NH}_3\) translates to stronger base characteristics compared to \(\text{NF}_3\).

Ammonia vs Nitrogen Trifluoride

When comparing ammonia (\(\text{NH}_3\)) and nitrogen trifluoride (\(\text{NF}_3\)) as bases, it’s crucial to consider their structural and electronic differences. Ammonia, with nitrogen bonded to three hydrogen atoms, retains more of its electron density. This makes it highly capable of accepting protons, bolstering its strength as a base.
In contrast, nitrogen trifluoride has nitrogen bonded to three highly electronegative fluorine atoms, which pull electron density away from nitrogen. This reduces its ability to accept protons, weakening its status as a base.
Ultimately, \(\text{NH}_3\) is recognized as a stronger base than \(\text{NF}_3\) due to its greater ability to maintain electron density and efficiently donate its lone pair of electrons in chemical reactions.