Question

1. write lewis structures that obey the octet rule for each of the following: 3

a) chcl3 b) nh4+
c) h2co

Explanation:

Step1: Determine the valence electrons

• For \(CHCl_3\):

Carbon (\(C\)) has \(4\) valence electrons, hydrogen (\(H\)) has \(1\) valence electron, and chlorine (\(Cl\)) has \(7\) valence electrons.
Total valence electrons \(=4 + 1+3\times7=4 + 1+21 = 26\)

• For \(NH_4^+\):

Nitrogen (\(N\)) has \(5\) valence electrons, hydrogen (\(H\)) has \(1\) valence electron. Since it is \(NH_4^+\), we subtract \(1\) electron (due to the positive charge).
Total valence electrons \(=5+4\times1 - 1=5 + 4-1=8\)

• For \(H_2CO\):

Carbon (\(C\)) has \(4\) valence electrons, hydrogen (\(H\)) has \(1\) valence electron, and oxygen (\(O\)) has \(6\) valence electrons.
Total valence electrons \(=4+2\times1 + 6=4+2 + 6=12\)

Step2: Arrange the atoms and form bonds

• For \(CHCl_3\):

Carbon is the central atom. Connect \(C\) to \(H\) and three \(Cl\) atoms with single bonds. Each single bond uses \(2\) electrons. After forming \(4\) single bonds (\(4\times2 = 8\) electrons used), we distribute the remaining \(26 - 8=18\) electrons as lone pairs on \(Cl\) atoms. Each \(Cl\) atom gets \(6\) lone - pair electrons.

• For \(NH_4^+\):

Nitrogen is the central atom. Connect \(N\) to four \(H\) atoms with single bonds. We have used \(4\times2 = 8\) electrons (which is the total number of valence electrons for \(NH_4^+\)).

• For \(H_2CO\):

Carbon is the central atom. Connect \(C\) to two \(H\) atoms with single bonds (\(2\times2 = 4\) electrons used). Then connect \(C\) to \(O\) with a double bond (\(4\) electrons). We have used \(4 + 4=8\) electrons. The remaining \(12-8 = 4\) electrons are placed as two lone pairs on \(O\) atom.

Answer:

• a) For \(CHCl_3\): The Lewis structure has \(C\) in the center, single - bonded to \(H\) and three \(Cl\) atoms. Each \(Cl\) has three lone pairs.
• b) For \(NH_4^+\): The Lewis structure has \(N\) in the center, single - bonded to four \(H\) atoms.
• c) For \(H_2CO\): The Lewis structure has \(C\) in the center, single - bonded to two \(H\) atoms and double - bonded to \(O\) (with two lone pairs on \(O\)).