Nitrogen gas is an extremely stable molecule because of which of the following?
A.
Ionic bonds
B.
Hydrogen bonds
C.
Resonance bonds
D.
Triple covalent bonds
The Correct Answer and Explanation is:
The correct answer is D. Triple covalent bonds.
Explanation:
Nitrogen gas (N₂) is known for its exceptional stability, which is primarily due to the nature of the chemical bond between its two nitrogen atoms. The molecule is held together by a triple covalent bond. To understand why this bond contributes to the stability of nitrogen gas, it’s important to explore the nature of covalent bonds and specifically, triple covalent bonds.
- Covalent Bonds and Triple Bonds: A covalent bond is formed when two atoms share one or more pairs of electrons. In the case of nitrogen gas (N₂), each nitrogen atom shares three pairs of electrons with the other nitrogen atom. This sharing of six electrons results in a triple covalent bond. Triple covalent bonds consist of one sigma (σ) bond and two pi (π) bonds.
- Strength and Stability: Triple covalent bonds are significantly stronger than single or double covalent bonds due to the multiple overlapping electron pairs. This strength arises from the additional electron pairs that hold the two nitrogen atoms together more tightly, making the bond stronger and less reactive. The high bond dissociation energy required to break a triple bond contributes to the overall stability of the molecule.
- Bond Dissociation Energy: The bond dissociation energy is the amount of energy needed to break a bond between two atoms. For a triple bond, this energy is much higher compared to single or double bonds. In the case of nitrogen, the bond dissociation energy is about 945 kJ/mol, which is relatively high. This high energy requirement means that the nitrogen molecule is less likely to react with other substances, contributing to its stability.
- Molecular Orbital Theory: According to molecular orbital theory, the formation of a triple bond results in the creation of a molecular orbital that stabilizes the molecule by lowering its overall energy. The overlapping of orbitals in a triple bond creates a strong and stable bond.
In contrast, the other options do not accurately explain the stability of nitrogen gas:
- Ionic bonds are formed through the transfer of electrons and are not applicable to nitrogen gas, which involves covalent bonding.
- Hydrogen bonds are a type of weak intermolecular force, not a bond within the molecule itself.
- Resonance bonds involve delocalized electrons in molecules with multiple structures, but nitrogen gas does not exhibit resonance.
Thus, the stability of nitrogen gas is best attributed to its triple covalent bonds, which provide a robust and strong connection between the nitrogen atoms, making the molecule extremely stable.