The oxidation number of nitrogen (N) in ammonia (NH₃) is −3.
Here’s the breakdown: Understanding Oxidation Numbers: * Oxidation numbers represent the hypothetical charge an atom would have if all bonds were completely ionic. * They help us track electron distribution and changes in redox reactions.
Rules for Assigning Oxidation Numbers:
Free Elements: Elements in their standard state have an oxidation number of 0 (e.g., O₂, N₂, Fe).
Ions: The oxidation number of a monatomic ion is equal to its charge (e.g., Na⁺ = +1, Cl⁻ = -1).
Hydrogen: Usually +1, except in metal hydrides where it’s -1.
Oxygen: Usually -2, except in peroxides (like H₂O₂) where it’s -1.
Fluorine: Always -1.
Applying the Rules to NH₃:
Hydrogen: Each hydrogen atom has an oxidation number of +1.
Ammonia (NH₃): Since the overall molecule is neutral, the sum of the oxidation numbers must be 0.
- Let the oxidation number of nitrogen be ‘x’.
- x + 3(+1) = 0
- x + 3 = 0
- x = -3
Therefore, the oxidation number of nitrogen in NH₃ is -3.
Why is nitrogen’s oxidation number negative in ammonia?
+Nitrogen has a higher electronegativity than hydrogen. In NH₃, nitrogen attracts the shared electrons more strongly, resulting in a partial negative charge on nitrogen and partial positive charges on the hydrogens. This electron distribution leads to nitrogen having a -3 oxidation state.
How does the oxidation number of nitrogen change in other compounds?
+Nitrogen’s oxidation number varies widely depending on the compound. For example: * In N₂ (nitrogen gas), it’s 0. * In NO₂ (nitrogen dioxide), it’s +4. * In NH₄⁺ (ammonium ion), it’s -3 (similar to NH₃).
What is the significance of oxidation numbers in chemistry?
+Oxidation numbers are crucial for: * Identifying redox reactions: Changes in oxidation numbers indicate electron transfer. * Balancing redox equations: They help ensure mass and charge conservation. * Understanding bonding: They provide insights into electron distribution within molecules.
