Question

\(\mathrm{CCl}_{4}\) does not show hydrolysis but \(\mathrm{SiCl}_{4}\) is readily hydrolyzed becausc (1) Carbon cannot expand its octet but silicon can expand. (2) Electronegativity of carbon is higher than that of silicon. (3) IP of carbon is higher than that of silicon. (4) Carbon forms double bonds and triple bends but not silicon.

Short answer

Carbon cannot expand its octet but silicon can.

Step-by-step solution

Understand the Concept of Octet Expansion

Carbon in \(\text{CCl}_4\) cannot expand its octet because it does not have available d-orbitals. Silicon in \(\text{SiCl}_4\), on the other hand, can expand its octet because it has empty d-orbitals in its valence shell.

Analyze Electronegativity Difference

The electronegativity of carbon is higher than that of silicon. However, this alone does not explain the difference in hydrolysis behavior.

Consider Ionization Potential (IP)

The ionization potential of carbon is higher than that of silicon. This is also not the main reason for the different hydrolysis behaviors.

Check the Ability to Form Multiple Bonds

Carbon can form double and triple bonds, while silicon generally does not form stable multiple bonds. However, this too is not related to the hydrolysis process.

Conclusion

Given these points, the reason \(\text{CCl}_4\) does not readily hydrolyze while \(\text{SiCl}_4\) does is primarily because carbon cannot expand its octet but silicon can.

Key concepts

headline of the respective core concept

Octet expansion is a significant concept to explain why \(\text{CCl}_4\) does not hydrolyze but \(\mathrm{SiCl}_4\) does. Carbon, with its smaller atomic size and higher electronegativity, doesn't have available d-orbitals. This means carbon can't hold more than eight electrons in its valence shell — a limitation known as the octet rule. Carbon follows this rule strictly. Silicon, on the other hand, is in the third period and has access to empty 3d-orbitals. These extra orbitals allow silicon to hold more than eight electrons, meaning it can undergo octet expansion. This capability of silicon to expand its octet provides the necessary electron space to react with water, leading to hydrolysis.

headline of the respective core concept

Electronegativity is the tendency of an atom to attract electrons toward itself. In this case, carbon has a higher electronegativity (2.55) compared to silicon (1.90). While it’s true that carbon attracts electrons more strongly than silicon, this higher electronegativity alone does not explain why \(\mathrm{CCl}_4\) resists hydrolysis. The difference in hydrolysis behavior between \(\mathrm{CCl}_4\) and silicon tetrachloride is mainly rooted in the structural and orbital differences influenced by octet expansion, not solely by electronegativity.

headline of the respective core concept

Ionization potential (IP) refers to the energy required to remove an electron from an atom. Carbon has a higher ionization potential compared to silicon. This means it's harder to ionize carbon, indicating a stronger hold on its electrons. While this is a property worth noting, it is not the primary factor affecting the hydrolysis of \(\text{CCl}_4\). The hydrolysis difference is more directly explained by the octet expansion capabilities of silicon rather than by the ionization potentials of carbon and silicon.

headline of the respective core concept

Multiple bonds are formed when two atoms share more than one pair of electrons. Carbon can form stable double and triple bonds due to its small size and suitable orbital overlap, which allows for effective π-bonding. Silicon, being larger and with a different orbital structure, generally does not form stable multiple bonds. However, the difference in the ability to form multiple bonds does not directly influence hydrolysis behavior of \(\text{CCl}_4\) versus \(\mathrm{SiCl}_4\). The lack of hydrolysis in \(\mathrm{CCl}_4\) is primarily due to carbon's inability to expand its octet, rather than its ability to form multiple bonds.