Question

Both \(\mathrm{NF}_{3}\) and \(\mathrm{NCl}_{3}\) are covalent but they differ in the extent of hydrolysis because (a) Cl can expand its octet by using d-orbitals (b) electronegativity of \(\mathrm{F}\) is greater than that of \(\mathrm{Cl}\) (c) dipole moment of \(\mathrm{NF}_{3}\) is greater than that of \(\mathrm{NCl}_{3}\) (d) \(\mathrm{NF}_{3}\) is more stable than \(\mathrm{NCl}_{3}\) and hydrolysis product of \(\mathrm{NF}_{3}\), HFO does not exist.

Short answer

The correct answer is (a): Cl can expand its octet by using d-orbitals.

Step-by-step solution

Analyze the Covalent Nature of NF3 and NCl3

Both NF3 and NCl3 are covalent compounds, meaning they share electrons between nitrogen and the halogen atoms. However, their reactivity and behavior in chemical reactions can differ based on the characteristics of the halogens involved, such as the ability to form multiple bonds and the availability of d-orbitals.

Evaluate the Role of d-Orbitals in Chlorine

Chlorine can use its d-orbitals to expand its valence shell beyond eight electrons. This expansion allows Cl to participate more effectively in chemical reactions such as hydrolysis. Fluorine does not possess d-orbitals in the same energy level to expand its octet.

Compare Electronegativity of Halogens

Fluorine has a higher electronegativity than chlorine, which affects bond polarity and the ability of molecules to participate in hydrolysis reactions. However, the primary difference in hydrolysis is not directly due to electronegativity.

Consider the Stability of NF3 and NCl3

NF3 is more stable due to the strength of the N-F bond compared to the N-Cl bond. Additionally, NF3 is less willing to undergo hydrolysis, making its hydrolysis product, HFO, less likely to exist. NCl3, on the other hand, can hydrolyze more readily due to weaker N-Cl bonds and the ability of Cl to expand its octet.

Identify the Correct Option Based on Hydrolysis Behavior

Considering the differences in octet expansion due to d-orbitals available in chlorine, (a) is the correct answer. This is because Cl can expand its octet by using d-orbitals, allowing NCl3 to hydrolyze more extensively than NF3.

Key concepts

Hydrolysis

Hydrolysis is an intriguing reaction where water molecules are used to break down compounds. In chemistry, it’s like adding water to split a molecule. For compounds like \(\mathrm{NF}_3\) and \(\mathrm{NCl}_3\), hydrolysis occurs at differing extents due to the inherent properties of the elements involved.
Chlorine, for instance, can open up to more expansive reactions with water compared to fluorine. While both form bonds with nitrogen, the capacity of chlorine to utilize its d-orbitals plays a critical role in how \(\mathrm{NCl}_3\) undergoes hydrolysis. This results in chlorine’s ability to bond with additional oxygen within the water, leading to more complete hydrolysis, unlike its counterpart, \(\mathrm{NF}_3\).
This makes hydrolysis a key concept in differentiating how molecular bonds choose to interact with water and undergo decomposition processes.

Electronegativity

Electronegativity is all about the thirst of an atom for electrons. It's like a tug of war between atoms vying for ownership of shared electrons. This concept is vital when understanding the bond characteristics of \(\mathrm{NF}_3\) and \(\mathrm{NCl}_3\).
In the periodic table, fluorine is the most electronegative element, which means it pulls strongly on electrons when forming bonds. This plays a big role in the stability of \(\mathrm{NF}_3\) as the nitrogen-fluorine bond is quite strong because of fluorine's high electronegativity.
Comparatively, chlorine is less electronegative than fluorine, resulting in a weaker hold on the electrons it shares with nitrogen in \(\mathrm{NCl}_3\). Though this weakens the bond, it also opens the door for chlorine to participate more readily in reactions such as hydrolysis. So, electronegativity not only determines bond strength but also how elements behave in the presence of water.

Octet Expansion

The concept of octet expansion allows certain elements to have more than eight electrons in their valence shell. Chlorine can do this trick, using its d-orbitals to consistently accommodate and play with additional electrons.
Unlike fluorine, which adheres strictly to the rule of eight due to its lack of d-orbitals, chlorine can expand its electrons beyond this point. This capacity for octet expansion means that compounds like \(\mathrm{NCl}_3\) can partake in a greater variety of chemical reactions, as seen in hydrolysis.
While fluorine is covalently rigid and cannot expand its bonds, chlorine’s ability to stretch its electron cloud allows more flexible interactions with other molecules, enhancing its reactivity.

D-Orbitals

D-orbitals offer an opportunity for atoms beyond the second period in the periodic table to expand their valences. For elements such as chlorine, these d-orbitals are like additional storage for electrons.
When chlorine forms bonds in \(\mathrm{NCl}_3\), it can make use of these d-orbitals to expand its valence shell. This expanded octet allows chlorine to create more complex interactions, particularly facilitating reactions like hydrolysis.
Fluorine, lacking d-orbitals, cannot expand its valence shell, keeping it more restricted. This means \(\mathrm{NF}_3\) does not react with water as easily as \(\mathrm{NCl}_3\) does. D-orbitals, therefore, play a critical role in explaining why \(\mathrm{NCl}_3\) shows a greater tendency towards such reactions.