To create a Lewis dot diagram for CHCl3, also known as chloroform, we need to follow a series of steps that involve determining the total number of valence electrons, drawing the skeletal structure, and then distributing the electrons to satisfy the octet rule for each atom, where possible.
Step 1: Determine the Total Number of Valence Electrons
- Carbon © has 4 valence electrons.
- Hydrogen (H) has 1 valence electron.
- Chlorine (Cl) has 7 valence electrons. Given that CHCl3 consists of 1 carbon, 1 hydrogen, and 3 chlorine atoms, the total number of valence electrons is calculated as follows: [4 © + 1 (H) + 3 \times 7 (Cl) = 4 + 1 + 21 = 26]
Step 2: Draw the Skeletal Structure
The least electronegative atom, which is carbon in this case (except for hydrogen), is typically placed in the center. Hydrogen is bonded directly to carbon, and the three chlorine atoms are also bonded to carbon, as carbon can form four bonds. The skeletal structure looks like this: [H - C - Cl] [|] [Cl] [|] [Cl]
Step 3: Distribute Electrons to Satisfy the Octet Rule
The carbon atom has four bonds (to one hydrogen and three chlorines), which means it effectively uses all its valence electrons to form these bonds. Each bond is a shared pair of electrons. For carbon, this looks like: [H : C : Cl :] [|] [: Cl :] [|] [: Cl :] However, each chlorine needs to satisfy the octet rule, which means each should have eight electrons in its outer shell. Since each chlorine forms a single bond with carbon, it only shares one pair of electrons with carbon. The remaining electrons are distributed as lone pairs on each chlorine atom: [H : C : Cl :] [|] [: Cl :] [|] [: Cl :] Each chlorine, having shared one pair with carbon (2 electrons), needs six more electrons to achieve an octet (eight electrons). These are represented as three lone pairs (6 electrons) on each chlorine atom.
Step 4: Finalize the Lewis Structure
After distributing all the valence electrons, the final Lewis dot structure for CHCl3 should show the carbon atom bonded to one hydrogen atom and three chlorine atoms, with each chlorine atom having three lone pairs of electrons to satisfy the octet rule.
[H - C - \overset{\cdot\cdot\cdot}{Cl}] [|] [\overset{\cdot\cdot\cdot}{Cl}] [|] [\overset{\cdot\cdot\cdot}{Cl}]
Each dot represents an electron. This structure shows carbon using all its valence electrons to form four single bonds (which satisfies its octet because it has no lone pairs but four bonds), hydrogen having two electrons to form a single bond with carbon (and no lone pairs), and each chlorine having three lone pairs (six electrons) in addition to the two electrons it shares with carbon in a single bond, thus each atom adhering to the octet rule where chemically possible.
This representation captures the essential electronic structure of chloroform, illustrating how the valence electrons are distributed to form bonds and satisfy the stability criteria for each atom in the molecule.
