Which of the following atoms is ${\mathrm{sp}}^2$ hybridized?

• A. The carbon atom in ethene ($C_2{H}_4$)
• B. The oxygen atom in water ($H_{2}O$)
• C. The nitrogen atom in ammonia (${\mathrm{NH}}_3$)
• D. The carbon atom in methane (${\mathrm{CH}}_4$)

Answer: (A)

Verified step by step guidance

1. Recall that sp² hybridization occurs when an atom forms three sigma bonds or has three regions of electron density, typically involving one unhybridized p orbital that participates in a pi bond.
2. Examine the carbon atom in ethene (C₂H₄): each carbon forms three sigma bonds (two with hydrogens and one with the other carbon) and one pi bond (the double bond between the carbons), which corresponds to sp² hybridization.
3. Consider the oxygen atom in water (H₂O): oxygen forms two sigma bonds with hydrogens and has two lone pairs, resulting in four regions of electron density, which corresponds to sp³ hybridization, not sp².
4. Look at the nitrogen atom in ammonia (NH₃): nitrogen forms three sigma bonds with hydrogens and has one lone pair, totaling four regions of electron density, indicating sp³ hybridization.
5. Analyze the carbon atom in methane (CH₄): carbon forms four sigma bonds with hydrogens, which corresponds to sp³ hybridization.