Based on the Lewis structure for SiF6^2-, what is the formal charge of the central silicon atom? QUESTION: What is the formal charge of the central silicon atom? Click “Submit” to submit your answer.
The Correct Answer and Explanation is:
The correct answer is e. -2.
Explanation
Formal charge is a concept used in chemistry to help determine the most plausible Lewis structure for a molecule or ion by assigning a hypothetical charge to each atom. It represents the charge an atom would have if all bonding electrons were shared equally between the a_toms. The calculation for formal charge follows a specific formula:
Formal Charge = (Number of Valence Electrons) – (Number of Non-bonding Electrons) – (½ × Number of Bonding Electrons)
To find the formal charge of the central silicon (Si) atom in the provided Lewis structure for the hexafluorosilicate ion (SiF6^2-), we can apply this formula step by step. Note that while the question text in the image incorrectly states SiF5^-, the Lewis structure drawn clearly shows a silicon atom bonded to six fluorine atoms, which corresponds to SiF6^2-. We must analyze the structure as it is drawn.
- Determine the Number of Valence Electrons for Silicon: Silicon (Si) is in Group 14 of the periodic table. Therefore, a neutral silicon atom has 4 valence electrons.
- Count the Non-bonding Electrons on Silicon: Looking at the Lewis structure, the central silicon atom has no lone pairs of electrons. So, the number of non-bonding electrons is 0.
- Count the Bonding Electrons around Silicon: The silicon atom is forming six single covalent bonds, one with each of the six fluorine atoms. Since each single bond consists of 2 electrons, the total number of bonding electrons around the central silicon atom is 6 bonds × 2 electrons/bond = 12 bonding electrons.
- Calculate the Formal Charge: Now, we plug these values into the formal charge formula:Formal Charge (Si) = 4 (Valence e-) – 0 (Non-bonding e-) – (½ × 12 Bonding e-)
Formal Charge (Si) = 4 – 0 – 6
Formal Charge (Si) = -2
Therefore, based on the given Lewis structure, the formal charge on the central silicon atom is -2.
