Question

the correct dot formulation for nitrogen trichloride has:
a 2 n - cl bonds, 1 n = cl bond and 8 lone pairs of electrons.
b 3 n = cl bonds and 6 lone pairs of electrons.
c 3 n - cl bonds and 9 lone pairs of electrons.
d 1 n - cl bond, 2 n = cl bonds and 7 lone pairs of electrons.
e 3 n - cl bonds and 10 lone pairs of electrons.

Explanation:

Step1: Determine the valence electrons

Nitrogen (\(N\)) has \(5\) valence electrons (\(2s^{2}2p^{3}\)), and chlorine (\(Cl\)) has \(7\) valence electrons (\(3s^{2}3p^{5}\)). For \(NCl_{3}\), the total number of valence electrons is \(5+(3\times7)=26\)

Step2: Draw the Lewis structure

Nitrogen is the central atom. Nitrogen forms single bonds (\(N - Cl\)) with three chlorine atoms. Each \(N - Cl\) bond uses \(2\) electrons. So, \(3\times2 = 6\) electrons are used in bonding.
The remaining electrons are \(26 - 6=20\) electrons. These are distributed as lone pairs. Nitrogen has \(1\) lone pair (\(2\) electrons), and each chlorine atom has \(3\) lone pairs (\(3\times3\times2 = 18\) electrons). The total number of lone - pair electrons is \(1 + 3\times3=10\) lone pairs (since each lone pair is \(2\) electrons, \(10\times2=20\) electrons which matches the remaining electron count). And there are \(3\) \(N - Cl\) single bonds.

Answer:

E. 3 N - Cl bonds and 10 lone pairs of electrons.