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:

Identify the steric number of the central atom

$$ \text{Steric Number} = \text{Number of single bonds} + \text{Number of lone pairs} = 3 + 1 = 4 $$

Determine the electron-pair geometry

$$ \text{Steric Number} = 4 \implies \text{Tetrahedral electron-pair geometry} $$

Determine the molecular shape

$$ \text{3 bonding pairs} + \text{1 lone pair} \implies \text{Trigonal pyramidal molecular geometry} $$

Answer:

• A) linear
• B) trigonal planar
• C) tetrahedral
• D) trigonal pyramidal (Correct answer)