Question

More than four bonds are made by how many elements in carbon family?

• A. 1
• B. 2
• C. 3
• D. 4
• E. 5

Hint:

Expansion of octet is only possible for elements from the 3rd period onwards. Carbon is the "odd one out" in its family for this property.

Answer 1

The Correct Option is D

Concept: The carbon family (Group 14) consists of C, Si, Ge, Sn, and Pb. The ability to form more than four bonds (expand covalency) depends on the presence of vacant \(d\)-orbitals.

Step 1: Evaluate Carbon.
Carbon is in the 2nd period. It has only \(2s\) and \(2p\) orbitals. It cannot expand its octet and is strictly limited to a maximum of 4 bonds.

Step 2: Evaluate Silicon, Germanium, Tin, and Lead.
These elements are in the 3rd, 4th, 5th, and 6th periods respectively. All of them have vacant \(d\)-orbitals available in their valence or outer shells.

Step 3: Identify higher coordination.
Because of the \(d\)-orbitals, Si, Ge, Sn, and Pb can form species with coordination numbers of 5 or 6 (e.g., \([SiF_6]^{2-}\), \([GeCl_6]^{2-}\), \([Sn(OH)_6]^{2-}\)). This means 4 out of the 5 main elements can make more than four bonds.