Construct the Lewis structure model for the covalent compound carbon tetrachloride (CCl4) using the following steps: The total number of valence electrons in CCl4 is 32. Write the atomic core for the element that seems most likely to be the central atom in the molecule in the space below. Position the remaining atomic cores around it. Place a bonding electron pair between each of the bonding atoms.
The Correct Answer and Explanation is:
Correct Lewis Structure for CCl₄ (Carbon Tetrachloride):
- Total Valence Electrons:
- Carbon (C) has 4 valence electrons.
- Each Chlorine (Cl) has 7 valence electrons.
- Total = 4 (from C) + 4 × 7 (from Cl) = 4 + 28 = 32 valence electrons.
- Choosing the Central Atom:
Carbon is the less electronegative atom compared to chlorine and can form four bonds, making it the most suitable central atom. - Sketching the Basic Framework:
Place the carbon atom at the center. Surround it with four chlorine atoms, one on each side. markdownCopyEditCl | Cl — C — Cl | Cl - Bonding Electrons:
Form a single bond between carbon and each chlorine atom. Each bond contains 2 electrons.- 4 bonds × 2 electrons = 8 electrons used.
- Distribute Remaining Electrons:
- 32 total valence electrons – 8 bonding electrons = 24 electrons left.
- Distribute these 24 electrons as lone pairs on the chlorine atoms (each Cl gets 6 electrons or 3 lone pairs).
- Final Structure:
Each chlorine has a full octet (1 bond + 3 lone pairs = 8 electrons). Carbon is bonded to 4 atoms (8 electrons total), fulfilling the octet rule.
Explanation
Carbon tetrachloride (CCl₄) is a molecular compound formed through covalent bonding. To construct its Lewis structure, we begin by determining the total number of valence electrons. Carbon has 4 valence electrons, and each chlorine atom contributes 7. With one carbon and four chlorine atoms, the total is 4 + 28 = 32 valence electrons.
Next, we determine the central atom. In covalent molecules, the least electronegative element typically becomes the central atom because it can form the most bonds. Carbon is less electronegative than chlorine and can form four bonds, making it the ideal central atom.
We then place the carbon atom at the center and position the four chlorine atoms symmetrically around it. A single bond is placed between the central carbon atom and each chlorine atom. Each single bond consists of two electrons, using up 8 of the 32 valence electrons. The remaining 24 electrons are distributed as lone pairs on the chlorine atoms. Each chlorine gets three lone pairs, which together with the single bond gives them a complete octet.
Carbon, through its four single bonds with chlorine, also satisfies the octet rule by having 8 shared electrons. The resulting structure is stable and symmetrical. The molecular shape of CCl₄ is tetrahedral, with bond angles of approximately 109.5 degrees. This geometry minimizes repulsion between bonding electron pairs, as described by VSEPR theory.
Thus, the Lewis structure for CCl₄ shows carbon in the center, bonded to four chlorine atoms with each chlorine having three lone pairs, ensuring all atoms follow the octet rule.
