Covalency of n in hno3 is 4 or 5 ??? Urgent....I have a exam tomorrow plz reply soon

The covalency of nitrogen in nitric acid (HNO3) is actually 5. Let’s break this down to understand why that is the case.

Covalency Explained

Covalency refers to the number of bonds an atom can form with other atoms. In the case of nitrogen, its typical covalency can vary depending on the molecule it's part of. Nitrogen has five valence electrons and can form bonds by sharing these electrons.

Structure of Nitric Acid

Nitric acid (HNO3) has a specific molecular structure that influences the covalency of nitrogen. The structure consists of one nitrogen atom bonded to three oxygen atoms and one hydrogen atom. To visualize this:

• The nitrogen atom is in the center.
• One oxygen atom forms a double bond with nitrogen.
• Another oxygen atom is connected through a single bond and carries a negative charge.
• The hydrogen atom is bonded to the negatively charged oxygen atom.

Analyzing Nitrogen's Bonds

In HNO3, nitrogen forms the following bonds:

• One double bond with one oxygen (contributing 2 to covalency).
• One single bond with another oxygen (contributing 1 to covalency).
• One bond with hydrogen (contributing 1 to covalency).

Now, if we add these contributions together, we have:

• Double bond (2) + Single bond (1) + Hydrogen bond (1) = 4 bonds

However, it’s important to consider the resonance structures of HNO3, which show that the nitrogen atom can effectively interact with multiple oxygen atoms, leading to a formal charge distribution that reflects a total of 5 effective bonds when considering resonance. This is why we say nitrogen has a covalency of 5 in this context.

Final Thoughts

So, to summarize, while it may look like nitrogen forms four bonds directly, the resonance and overall bonding interactions in HNO3 lead us to conclude that nitrogen's covalency is indeed 5. This understanding can help you with other nitrogen-containing compounds as well, where covalency can vary based on the molecular structure and bonding environment. Good luck with your exam!