Textbook Question
Identify the group 5A element that best fits each of the following descriptions.
(a) Forms strong π bonds
Ch.22 - The Main Group Elements
Chapter 22, Problem 108
Draw an electron-dot structure for N2, and explain why this molecule is so unreactive.
Verified step by step guidance1
Step 1: Identify the total number of valence electrons in the N2 molecule. Each nitrogen atom has 5 valence electrons, so for N2, the total is 5 + 5 = 10 valence electrons.
Step 2: Arrange the nitrogen atoms side by side and begin by placing a single bond (a pair of electrons) between them. This accounts for 2 of the 10 valence electrons.
Step 3: Distribute the remaining valence electrons to satisfy the octet rule for each nitrogen atom. Since each nitrogen atom needs 8 electrons to complete its octet, add two more pairs of electrons (4 electrons) between the nitrogen atoms to form a triple bond.
Step 4: Verify that each nitrogen atom has a complete octet. With a triple bond, each nitrogen atom shares 6 electrons, and each has 2 non-bonding electrons, completing the octet.
Step 5: Explain the unreactivity of N2. The triple bond in N2 is very strong and requires a significant amount of energy to break, making the molecule very stable and unreactive under normal conditions.
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Electron-Dot Structure
An electron-dot structure, or Lewis structure, represents the valence electrons of atoms within a molecule. In this diagram, dots are used to illustrate the bonding between atoms and the presence of lone pairs. For nitrogen (N2), the structure shows a triple bond between the two nitrogen atoms, indicating that they share three pairs of electrons, which contributes to the molecule's stability.
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Triple Bond
A triple bond occurs when two atoms share three pairs of electrons, resulting in a strong bond. In the case of N2, the triple bond between the nitrogen atoms is very strong due to the effective overlap of their p-orbitals. This strong bonding interaction makes the molecule less likely to react with other substances, as breaking the triple bond requires a significant amount of energy.
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Molecular Stability and Reactivity
Molecular stability refers to the tendency of a molecule to maintain its structure without undergoing chemical change. N2 is particularly unreactive due to its strong triple bond and the lack of available lone pairs for bonding with other atoms. This stability is a key reason why nitrogen gas is inert under standard conditions, making it a common filler gas in various applications.
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