Question

1. this is a diagram of ammonia. this molecule has a central nitrogen atom singly bonded to three hydrogen atoms. the nitrogen atom also has one lone pair of electrons. the shape of this molecule can be classified as _______. a) linear b) trigonal planar c) tetrahedral d) trigonal pyramidal

Explanation:

To determine the molecular shape of ammonia ($\ce{NH_3}$), we analyze the central nitrogen atom. Nitrogen has 5 valence electrons. In $\ce{NH_3}$, it forms three single bonds with hydrogen atoms (using 3 electrons) and has one lone pair (2 electrons). The electron - pair geometry (considering both bonding and lone pairs) is tetrahedral because there are 4 electron groups (3 bonding, 1 lone pair). However, the molecular shape (considering only the positions of the atoms) is determined by the arrangement of the bonding pairs around the central atom, with the lone pair influencing the shape. A molecule with a central atom having 3 bonding pairs and 1 lone pair has a trigonal pyramidal shape.

• Option A: Linear shape occurs when the atoms are arranged in a straight line, like in $\ce{CO_2}$ (central C with 2 double bonds and no lone pairs), which is not the case for $\ce{NH_3}$.
• Option B: Trigonal planar shape has the central atom with 3 bonding pairs and no lone pairs, like in $\ce{BF_3}$, but $\ce{NH_3}$ has a lone pair, so this is incorrect.
• Option C: Tetrahedral is the electron - pair geometry of $\ce{NH_3}$, but the molecular shape (the shape of the atoms) is not tetrahedral as there is a lone pair that is not an atom.
• Option D: Trigonal pyramidal is the correct molecular shape for $\ce{NH_3}$ as the three hydrogen atoms form a pyramid - like structure around the central nitrogen with the lone pair at the top of the pyramid - like arrangement.

Answer:

D) trigonal pyramidal