Question

Determine the formal charge of each element in the following:

(a) $\mathrm{H}\mathrm{C}\mathrm{l}$

(b) $\mathrm{C}{\mathrm{F}}_4$

(c) $\mathrm{P}\mathrm{C}{\mathrm{l}}_3$

(d) $\mathrm{P}{\mathrm{F}}_5$

Short answer

(a) The formal charge of $\mathrm{H}$ and $\mathrm{C}\mathrm{l}$ in the compound $\mathrm{H}\mathrm{C}\mathrm{l}$ is $0$.

(b) The formal charge of $\mathrm{C}$and $\mathrm{F}$ in the compound $\mathrm{C}{\mathrm{F}}_4$ is $0$.

(c) The formal charge of $\mathrm{P}$ and $\mathrm{C}\mathrm{l}$ in the compound $\mathrm{P}\mathrm{C}{\mathrm{l}}_3$ is $0$.

(d) The formal charge of $\mathrm{P}$and $\mathrm{F}$ in the compound $\mathrm{P}{\mathrm{F}}_5$ is $0$.

Step-by-step solution

Concept Introduction

A formal charge ($\mathrm{F}.\mathrm{C}.$or$\mathrm{q}$) is the charge attributed to an atom in a molecule in the covalent perspective of bonding, assuming that electrons in all chemical bonds are shared equally among atoms, regardless of relative electronegativity.

Formal Charge of Hydrogen Chloride

a)

To find the Formal charge use the formula –

Formal Charge $=$ $($Number of valence electrons on atom) $-$ (non-bonded electrons $+$ Bonding electrons$)$.

Formal Charge for$\mathrm{H}$ is:

$\begin{array}{rl}& =\left(1\right)-\left(0+1\right)\\ & =0\end{array}$

Formal Charge for$\mathrm{C}\mathrm{l}$is:

$\begin{array}{rl}& =\left(7\right)-\left(6+1\right)\\ & =0\end{array}$

The formal charge for $\mathrm{H}\mathrm{C}\mathrm{l}$ is found below –

Element	Bonding Electrons	Non-bonded Electrons	Valence Electrons	Formal Charge
$\mathrm{H}$	$1$	$0$	$1$	$0$
$\mathrm{C}\mathrm{l}$	$1$	$6$	$7$	$0$

Therefore, the formal charge for $\mathrm{H}$ and$\mathrm{C}\mathrm{l}$ is $0$.

Formal Charge of Carbon Tetrafluoride

(b)

To find the Formal charge use the formula –

Formal Charge$=$ $($Number of valence electrons on atom) $-$ (non-bonded electrons $+$Bonding electrons$)$.

Formal Charge for$\mathrm{C}$ is:

$\begin{array}{rl}& =\left(4\right)-\left(0+4\right)\\ & =0\end{array}$

Formal Charge for $\mathrm{F}$ is:

$\begin{array}{rl}& =\left(7\right)-\left(6+1\right)\\ & =0\end{array}$

The formal charge for $\mathrm{C}{\mathrm{F}}_4$ is found below –

Element	Bonding Electrons	Non-bonded Electrons	Valence Electrons	Formal Charge
$\mathrm{C}$	$4$	$0$	$4$	$0$
$\mathrm{F}$	$1$	$6$	$7$	$0$

Therefore, the formal charge for$\mathrm{C}$and$\mathrm{F}$is$0$.

Formal Charge of Phosphorus Trichloride

(c)

To find the Formal charge use the formula –

Formal Charge$=$ $($Number of valence electrons on atom) $-$ (non-bonded electrons $+$Bonding electrons$)$.

Formal Charge for $\mathrm{P}$ is:

$\begin{array}{rl}& =\left(5\right)-\left(2+3\right)\\ & =0\end{array}$

Formal Charge for $\mathrm{C}\mathrm{l}$is:

$\begin{array}{rl}& =\left(7\right)-\left(6+1\right)\\ & =0\end{array}$

The formal charge for$\mathrm{P}\mathrm{C}{\mathrm{l}}_3$ is found below –

Element	Bonding Electrons	Non-bonded Electrons	Valence Electrons	Formal Charge
$\mathrm{P}$	$3$	$2$	$5$	$0$
$\mathrm{C}\mathrm{l}$	$1$	$6$	$7$	$0$

Therefore, the formal charge for$\mathrm{P}$ and $\mathrm{C}\mathrm{l}$ is $0$.

Formal Charge of Phosphorus Pentafluoride

(d)

To find the Formal charge use the formula –

Formal Charge$=$ $($Number of valence electrons on atom)$-$ (non-bonded electrons $+$ Bonding electrons$)$.

Formal Charge for $\mathrm{P}$ is:

$\begin{array}{rl}& =\left(5\right)-\left(0+5\right)\\ & =0\end{array}$

Formal Charge for$\mathrm{F}$is:

$\begin{array}{rl}& =\left(7\right)-\left(6+1\right)\\ & =0\end{array}$

The formal charge for$\mathrm{P}{\mathrm{F}}_5$ is found below –

Element	Bonding Electrons	Non-bonded Electrons	Valence Electrons	Formal Charge
$\mathrm{P}$	$5$	$0$	$5$	$0$
$\mathrm{F}$	$1$	$6$	$7$	$0$

Therefore, the formal charge for$\mathrm{P}$ and$\mathrm{F}$is$0$.