Consider the Lewis structure of CF_(4). What is the formal charge on the central carbon atom? Consider the Lewis structure of CF4. What is the formal charge on the central carbon atom? O-2 O+4 00 O+2 O-1 O+1 -4
The Correct Answer and Explanation is:
The correct answer is 0 — the formal charge on the central carbon atom in the Lewis structure of CF₄ is zero.
To understand why, let’s analyze the molecule in detail:
Carbon tetrafluoride (CF₄) consists of a central carbon atom covalently bonded to four fluorine atoms. Each fluorine atom forms a single bond with carbon, and each has three lone pairs of electrons, satisfying the octet rule. Carbon, in turn, uses all four of its valence electrons to form these four single bonds, also completing its octet.
To calculate formal charge, we use the formula:
Formal charge = Valence electrons − (Nonbonding electrons + ½ × Bonding electrons)
For the carbon atom in CF₄:
- Valence electrons of carbon: 4 (as carbon is in group 14)
- Nonbonding electrons on carbon: 0 (all electrons are in bonds)
- Bonding electrons around carbon: 8 (from four single bonds)
Plugging into the formula:
Formal charge = 4 − (0 + ½ × 8) = 4 − 4 = 0
This result means the carbon atom is neutral in this configuration, which contributes to the stability of the molecule. Formal charge calculations are crucial in assessing the most reasonable Lewis structures, as structures with formal charges closest to zero are generally more stable and likely to represent the actual electron distribution.
Although each fluorine atom carries more electronegative power, the overall symmetry and equal electron distribution in CF₄ result in a nonpolar molecule with no formal charge on the central atom. Recognizing this reinforces key concepts in bonding and molecular geometry, such as octet fulfillment, electronegativity, and resonance stability.
