The correct formula used to determine the formal charge $\left(\mathrm{Q}_{\mathrm{f}}\right)$ on an atom in…

The correct formula used to determine the formal charge $\left(\mathrm{Q}_{\mathrm{f}}\right)$ on an atom in the given Lewis structure of a molecule or ion is ( $\mathrm{V}=$ number of valence electrons in free atom, $\mathrm{U}=$ number of unshared electrons on the atom, $\mathrm{B}=$ number of bonds around the atom)
  1. $\mathrm{Q}_{\mathrm{f}}=\mathrm{V}-\left(\frac{\mathrm{U}}{\mathrm{B}}\right)$
  2. $\mathrm{Q}_{\mathrm{f}}=\mathrm{V}+(\mathrm{U}-\mathrm{B})$
  3. $\mathrm{Q}_{\mathrm{f}}=\mathrm{V}-(\mathrm{U}+\mathrm{B})$
  4. $\mathrm{Q}_{\mathrm{f}}=\mathrm{V}-\left(\frac{\mathrm{B}}{\mathrm{U}}\right)$

Solution

Formal charge $\left(Q_f\right)$ on an atom $=[$ Total number of valence electron in the free atom (v)] -[total number of non bonding/unshared electron] -[number of bond around the atom] $\begin{aligned} & \therefore Q_f=V-(U)-(B) \\ & Q_f=V-(U+B)\end{aligned}$

Asked in: AP EAMCET 2024 (18 May Shift 1)

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