Ques 53 E - Chemistry (OpenStax)

Question

Calculate the formal charge of chlorine in the molecules \({\rm{C}}{{\rm{l}}_{\rm{2}}}\), \({\rm{BeC}}{{\rm{l}}_{\rm{2}}}\), and \({\rm{Cl}}{{\rm{F}}_{\rm{5}}}\).

Step-by-Step Solution

Answer

The formal charge of \({\rm{Cl}}\) in the compound \({\rm{C}}{{\rm{l}}_{\rm{2}}}\) is \(0\), \({\rm{Be}}\) and \({\rm{Cl}}\) in the compound \({\rm{BeC}}{{\rm{l}}_{\rm{2}}}\) is \(0\)and, \({\rm{Cl}}\) and \({\rm{F}}\) in the compound \({\rm{Cl}}{{\rm{F}}_{\rm{5}}}\) is \(0\).

Step 1: Concept Introduction

A formal charge (\({\rm{F}}{\rm{.C}}{\rm{.}}\) or \({\rm{q}}\)) is the charge on an atom/molecule in covalent bonding, assuming electrons are shared equally in bonds made.

Step 2: Formal Charge of Chlorine

To find the Formal charge use the formula –

Formal Charge \({\rm{ = }}\) \({\rm{(}}\)Number of valence electrons on atom) \({\rm{ - }}\) (non-bonded electrons \({\rm{ + }}\) Bonding electrons\({\rm{)}}\).

Formal Charge for \({\rm{Cl}}\) is: 

\(\begin{aligned}&= \left( 7 \right){\rm{ - }}\left( {{\rm{6 + 1}}} \right)\\&= 0\end{aligned}\)

The formal charge for \({\rm{C}}{{\rm{l}}_{\rm{2}}}\) is found below –

Element	Bonding Electrons	Non-bonded Electrons	Valence Electrons	Formal Charge
\({\rm{Cl}}\)	\(1\)	\(6\)	\(7\)	\(0\)

 

Therefore, the formal charge for \({\rm{Cl}}\) is \(0\).

Step 3: Formal Charge of Beryllium Chloride

To find the Formal charge use the formula –

Formal Charge \({\rm{ = }}\) \({\rm{(}}\)Number of valence electrons on atom) \({\rm{ - }}\) (non-bonded electrons \({\rm{ + }}\) Bonding electrons\({\rm{)}}\).

Formal Charge for \({\rm{Be}}\) is:

 \(\begin{aligned}&= \left( {\rm{2}} \right){\rm{ - }}\left( {{\rm{0 + 2}}} \right)\\&= \end{aligned}\)

Formal Charge for \({\rm{Cl}}\) is: 

\(\begin{aligned}&= \left( 7 \right){\rm{ - }}\left( {{\rm{6 + 1}}} \right)\\&= 0\end{aligned}\)

The formal charge for \({\rm{BeC}}{{\rm{l}}_{\rm{2}}}\) is found below –

Element	Bonding Electrons	Non-bonded Electrons	Valence Electrons	Formal Charge
\({\rm{Be}}\)	\(2\)	\(0\)	\(2\)	\(0\)
\({\rm{Cl}}\)	\(1\)	\(6\)	\(7\)	\(0\)

 

Therefore, the formal charge for \({\rm{Be}}\) and \({\rm{Cl}}\) is \(0\).

Step 4: Formal Charge of Chlorine Pentafluoride

To find the Formal charge use the formula –

Formal Charge \({\rm{ = }}\) \({\rm{(}}\)Number of valence electrons on atom) \({\rm{ - }}\) (non-bonded electrons \({\rm{ + }}\) Bonding electrons\({\rm{)}}\).

Formal Charge for \({\rm{Cl}}\) is: 

\(\begin{aligned} &= \left( 7 \right){\rm{ - }}\left( {{\rm{2 + 5}}} \right)\\&= 0\end{aligned}\)

Formal Charge for \({\rm{F}}\) is: 

\(\begin{aligned}&= \left( 7 \right){\rm{ - }}\left( {{\rm{6 + 1}}} \right)\\&= 0\end{aligned}\)

The formal charge for \({\rm{Cl}}{{\rm{F}}_{\rm{5}}}\) is found below –

Element	Bonding Electrons	Non-bonded Electrons	Valence Electrons	Formal Charge
\({\rm{Cl}}\)	\(5\)	\(2\)	\(7\)	\(0\)
\({\rm{F}}\)	\(1\)	\(6\)	\(7\)	\(0\)

 

Therefore, the formal charge for \({\rm{Cl}}\) and \({\rm{F}}\) is \(0\).