Which of the following statement about `Si` is correct.

Options

A. `Si` predominantly forms covalent componds with oxidation number as `+4`.
B. Ionisation enthalpy of `Si` is more than that of carbon.
C. Electron affinity of `Si` is less than that of carbon.
D. `Si` can't show coordination number more than `4`.

Answer

To determine which statement about silicon (Si) is correct, we will analyze each of the provided statements step by step.

### Step 1: Analyze the first statement
**Statement 1:** Silicon predominantly forms covalent compounds with oxidation number 4.

- Silicon is in group 14 of the periodic table, which means it has 4 valence electrons.
- Silicon can form covalent bonds by sharing these electrons, and it commonly exhibits an oxidation state of +4.
- According to Fajan's rule, elements with smaller sizes and higher positive charges tend to form covalent compounds. Silicon, with its +4 oxidation state, predominantly forms covalent compounds.

**Conclusion:** This statement is **correct**.

### Step 2: Analyze the second statement
**Statement 2:** Ionization enthalpy of silicon is more than that of carbon.

- Ionization enthalpy is the energy required to remove an electron from an atom.
- As we move down a group in the periodic table, atomic size increases, making it easier to remove the outermost electron.
- Since silicon is below carbon in group 14, it has a larger atomic size than carbon, which means it has a lower ionization enthalpy compared to carbon.

**Conclusion:** This statement is **incorrect**.

### Step 3: Analyze the third statement
**Statement 3:** Electron affinity of silicon is less than that of carbon.

- Electron affinity is the amount of energy released when an electron is added to a neutral atom.
- Generally, as we go down a group, electron affinity decreases. However, silicon has a vacant 3d orbital, which allows it to accommodate an additional electron more effectively than carbon.
- Therefore, silicon has a higher electron affinity than carbon.

**Conclusion:** This statement is **incorrect**.

### Step 4: Analyze the fourth statement
**Statement 4:** Si cannot show coordination number more than 4.

- Coordination number refers to the number of atoms or ions immediately surrounding a central atom in a complex or crystal.
- Silicon has vacant d orbitals, which allows it to expand its covalency beyond 4.
- Therefore, silicon can exhibit coordination numbers of up to 6.

**Conclusion:** This statement is **incorrect**.

### Final Conclusion
The only correct statement about silicon is the first one: "Silicon predominantly forms covalent compounds with oxidation number 4."

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