Draw on paper the Lewis structure for hypochlorous acid HOCI (oxygen is the central atom) and for hydrogen cyanide HCN. Calculate the formal charge for each atom in these compounds, and then label each atom in your drawing with its formal charge.
The correct answer and explanation is :
Lewis Structures and Formal Charges of HOCl and HCN
✅ LEWIS STRUCTURES (with formal charges labeled):
1. Hypochlorous acid (HOCl), with oxygen as the central atom:
H – O – Cl
.. ..- Hydrogen (H): 0 formal charge
- Oxygen (O): 0 formal charge
- Chlorine (Cl): 0 formal charge
2. Hydrogen cyanide (HCN):
H – C ≡ N:
..- Hydrogen (H): 0 formal charge
- Carbon (C): 0 formal charge
- Nitrogen (N): 0 formal charge
🧠 EXPLANATION (300+ words):
Lewis Structures and Formal Charges:
The Lewis structure of a molecule shows how atoms are bonded and where the valence electrons are located. To assess whether a Lewis structure is correct, we calculate formal charges for each atom using the formula:
[
\text{Formal charge} = \text{Valence electrons} – (\text{Lone pair electrons} + \frac{1}{2} \times \text{Bonding electrons})
]
🔍 1. HOCl (Hypochlorous acid)
Given that oxygen is the central atom, it forms a single bond with hydrogen and a single bond with chlorine. Oxygen also has two lone pairs, giving it a total of 6 valence electrons.
- H (1 valence e⁻): Bonded to O → 1 bond (2 shared electrons), no lone pairs
[
1 – (0 + 1) = 0
] - O (6 valence e⁻): 2 bonds (H and Cl) + 4 nonbonding electrons (2 lone pairs)
[
6 – (4 + 2) = 0
] - Cl (7 valence e⁻): 1 bond with O + 6 nonbonding electrons (3 lone pairs)
[
7 – (6 + 1) = 0
]
So, all atoms have a formal charge of 0, indicating a stable structure.
🔍 2. HCN (Hydrogen cyanide)
Here, carbon is the central atom. It forms a single bond with hydrogen and a triple bond with nitrogen. Nitrogen ends up with one lone pair, and carbon has no lone pairs.
- H (1 valence e⁻): One bond
[
1 – (0 + 1) = 0
] - C (4 valence e⁻): One single bond (H) + one triple bond (N) = 4 bonding pairs
[
4 – (0 + 4) = 0
] - N (5 valence e⁻): Triple bond + 1 lone pair (2 electrons)
[
5 – (2 + 3) = 0
]
Again, all formal charges are zero, confirming stability.
✅ Summary:
Both HOCl and HCN have zero formal charges on all atoms when drawn correctly, and this makes their Lewis structures both chemically stable and correct.