Question

Explain why the following Lewis structure is incorrect and identify the chemical formula for this molecule.H:C:C:H

a) The structure lacks octets for carbon atoms; the chemical formula is C2H2.

b) The structure lacks a double bond between carbon atoms; the chemical formula is CH3.

c) The structure contains too many hydrogen atoms; the chemical formula is C2H4.

d) The structure lacks lone pairs on carbon atoms; the chemical formula is CH2.

Answer 1

The provided Lewis structure H:C:C:H is incorrect because it fails to fulfill the octet rule for the carbon atoms. The corrected chemical formula is C2H2 and requires a triple bond between the carbon atoms to satisfy the rule.

Step-by-step explanation:

The incorrect Lewis structure presented, H:C:C:H, suggests a molecule with a single bond between the two carbon atoms and a single bond to each hydrogen atom. Given that carbon prefers to form four bonds to satisfy its octet, this structure lacks sufficient connectivity to fulfill the octet rule. The correct chemical formula for the molecule depicted by this structure is C2H2, making use of a triple bond between the carbon atoms and a single bond to each hydrogen, ensuring each carbon has an octet.

To correct the structure, we eliminate the lone pairs on the carbon atoms and have the carbon atoms share three pairs (a triple bond) instead of one pair of electrons. This modification satisfies the octet rule for both carbon atoms and the duet rule for the hydrogen atoms, resulting in an accurate Lewis structure for acetylene, C2H2.