Question

question 11
what is a major difference in structure between ch4 and nh3?
appearance of lone pairs of electrons
color of central atom
number of bonds on central atom
steric number

Explanation:

• For \(CH_4\): The central atom \(C\) has 4 valence electrons. It forms 4 \(C - H\) bonds. There are no lone pairs of electrons on the central \(C\) atom. The steric number (sum of \(\sigma\) - bonds and lone pairs) is \(4+0 = 4\), and it has a tetrahedral geometry.
• For \(NH_3\): The central atom \(N\) has 5 valence electrons. It forms 3 \(N - H\) bonds. There is 1 lone pair of electrons on the central \(N\) atom (\(5-(3\times1)=2\) electrons or 1 lone pair). The steric number is \(3 + 1=4\), and it has a trigonal - pyramidal geometry (due to the lone pair).
• The color of the central atom is not relevant in terms of structure (atoms are colorless in the context of molecular structure discussions).
• The number of bonds on the central atom: \(CH_4\) has 4 \(C - H\) bonds and \(NH_3\) has 3 \(N - H\) bonds. But the more fundamental difference related to structure (which is influenced by electron - pair repulsion) is the presence of lone pairs.
• The steric number for \(CH_4\) is 4 and for \(NH_3\) is also 4 (since steric number \(= \text{number of}\ \sigma-\text{bonds}+\text{number of lone pairs}\), \(4 = 4+0\) for \(CH_4\) and \(4=3 + 1\) for \(NH_3\)).

Answer:

Appearance of lone pairs of electrons.