Which of the following correctly describes the molecular geometry around the central atoms (nitrogen, alpha carbon, and carboxyl carbon) in the amino acid glycine (${\mathrm{NH}}_2\mathrm{CH}{2}_{}\mathrm{COOH}$)?

• A. Nitrogen: tetrahedral; alpha carbon: trigonal pyramidal; carboxyl carbon: trigonal planar
• B. Nitrogen: linear; alpha carbon: tetrahedral; carboxyl carbon: tetrahedral
• C. Nitrogen: trigonal pyramidal; alpha carbon: tetrahedral; carboxyl carbon: trigonal planar
• D. Nitrogen: trigonal planar; alpha carbon: trigonal planar; carboxyl carbon: tetrahedral

Answer: (C)

Verified step by step guidance

1. Identify the central atoms in glycine: the nitrogen in the amino group (NH\_2), the alpha carbon (the carbon attached to NH\_2 and COOH), and the carboxyl carbon (the carbon in the COOH group).
2. Determine the electron domain geometry around each central atom by counting the number of bonded atoms and lone pairs of electrons on that atom.
3. For nitrogen in NH\_2: it has three bonded atoms (two hydrogens and the alpha carbon) and one lone pair, which corresponds to a trigonal pyramidal geometry.
4. For the alpha carbon: it is bonded to four different groups (NH\_2, H, COOH, and the side chain which is H in glycine), so it has four bonded atoms and no lone pairs, corresponding to a tetrahedral geometry.
5. For the carboxyl carbon: it is bonded to three groups (one double bond to oxygen, one single bond to OH, and one single bond to the alpha carbon) and has no lone pairs, which corresponds to a trigonal planar geometry.