Formal Charges
Formal charges have an important role in organic chemistry since this concept helps us to know whether an atom in a molecule is neutral/bears a positive or negative charge. Even if some molecules are neutral, the atoms within that molecule need not be neutral atoms.
Polarity Of Water
In simple chemical terms, polarity refers to the separation of charges in a chemical species leading into formation of two polar ends which are positively charged end and negatively charged end. Polarity in any molecule occurs due to the differences in the electronegativities of the bonded atoms. Water, as we all know has two hydrogen atoms bonded to an oxygen atom. As oxygen is more electronegative than hydrogen thus, there exists polarity in the bonds which is why water is known as a polar solvent.
Valence Bond Theory Vbt
Valence bond theory (VBT) in simple terms explains how individual atomic orbitals with an unpaired electron each, come close to each other and overlap to form a molecular orbital giving a covalent bond. It gives a quantum mechanical approach to the formation of covalent bonds with the help of wavefunctions using attractive and repulsive energies when two atoms are brought from infinity to their internuclear distance.
![### Possible Structure of \( ClO_4^- \)
Below is an image depicting a possible Lewis structure for the perchlorate ion (\( ClO_4^- \)):
#### Structure A
- In this structure, a central chlorine (Cl) atom is bonded to four oxygen (O) atoms.
- Each oxygen atom forms a double bond with the central chlorine atom.
- The chlorine atom has no lone pairs, while each oxygen atom has four lone pairs.
- The entire structure carries a negative charge, represented by a minus sign outside a bracket enclosing the structure.
#### Question
What is the formal charge of the central Cl in this structure?
#### Answer Choices
- \(+3\)
- \(+2\)
- \(+1\)
- \(0\)
- \(-1\)
- \(-2\)
- \(-3\)
### Explanation on Formal Charge
To determine the formal charge of the central Cl atom in this structure, use the formal charge formula:
\[ \text{Formal Charge} = ( \text{Valence Electrons} ) - ( \text{Non-bonding Electrons} + \frac{1}{2} \text{Bonding Electrons} ) \]
For chlorine (Cl):
- Valence Electrons: 7 (since chlorine is in group 17 of the periodic table)
- Non-bonding Electrons: 0 (chlorine has no lone pairs in this structure)
- Bonding Electrons: 8 (chlorine forms double bonds with 4 oxygens, so 4 x 2 = 8)
Formal Charge Calculation for Cl:
\[ \text{Formal Charge} = 7 - (0 + \frac{1}{2} \times 8) \]
\[ = 7 - 4 \]
\[ = +3 \]
#### Conclusion
The formal charge of the central Cl in structure \( A \) is \( +3 \).](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Faf6c3174-f071-4892-a981-9c51afb6153d%2F5e371ab4-0ed0-4eac-88ca-54c086594717%2F53v8f6x_processed.png&w=3840&q=75)
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