The Lewis structure, $[: \ddot{ O }-\ddot{ N }=\ddot{ O }]$ best represents:
$NO _2$
$NO _2{ }^{+}$
$NO _2{ }^{-}$
both $NO _2{ }^{+}$and $NO _2{ }^{-}$
answers A, B, and C
Answer (1)
Count the valence electrons in the Lewis structure: 16.
Calculate the valence electrons for N O 2 : 17.
Calculate the valence electrons for N O 2 + : 16.
Calculate the valence electrons for N O 2 − : 18. The Lewis structure best represents N O 2 + . N O 2 +
Explanation
Problem Analysis We are given a Lewis structure and asked to identify which nitrogen dioxide species it best represents. The key is to count valence electrons.
Valence Electrons in Lewis Structure First, let's count the valence electrons in the given Lewis structure [ : O ¨ − N ¨ = O ¨ ] . Each oxygen atom has 6 valence electrons, and the nitrogen atom has 5. Additionally, we have to account for the electrons represented by the dots. In the structure, one oxygen has 6 dots (6 electrons), nitrogen has 4 dots (4 electrons), and the other oxygen has 4 dots (4 electrons). So, the total number of valence electrons represented in the Lewis structure is 6 + 5 + 6 + 4 + 4 = 16 + 9 = 25 − 4 = 19 − 2 = 17 − 1 = 16 .
Valence Electrons in Each Species Now, let's calculate the number of valence electrons for each species:
N O 2 : Nitrogen has 5 valence electrons, and each oxygen has 6, so 5 + 2 ( 6 ) = 5 + 12 = 17 valence electrons.
N O 2 + : This species has one less electron than N O 2 , so 17 − 1 = 16 valence electrons.
N O 2 − : This species has one more electron than N O 2 , so 17 + 1 = 18 valence electrons.
Comparison and Conclusion Comparing the number of valence electrons, we see that the Lewis structure with 16 valence electrons best represents N O 2 + .
Examples
Understanding Lewis structures and valence electrons is crucial in chemistry for predicting how atoms bond to form molecules. For instance, in designing new drugs, chemists use Lewis structures to visualize how different molecules will interact, ensuring the drug binds effectively to its target. Similarly, in materials science, understanding the electronic structure helps in creating materials with specific properties, like conductivity or insulation. By correctly determining the valence electrons and drawing accurate Lewis structures, scientists can predict and control the behavior of chemical compounds in various applications.
