Lewis Structure Chemistry Example 3

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Example 3

hard
Draw the Lewis structure for the nitrate ion (NO3−\text{NO}_3^-). Include formal charges.

Solution

  1. 1
    Total valence electrons: N has 5, each O has 6, plus 1 for the negative charge: 5+3(6)+1=245 + 3(6) + 1 = 24.
  2. 2
    Place N as central atom with one double bond to one O and single bonds to the other two O atoms. This uses 2+2(2)+2=82 + 2(2) + 2 = 8 electrons from bonds (actually 4 bonds = 8 electrons). Distribute remaining 16 as lone pairs.
  3. 3
    Formal charges: N = 5−0−4=+15 - 0 - 4 = +1, double-bonded O = 6−4−2=06 - 4 - 2 = 0, each single-bonded O = 6−6−1=−16 - 6 - 1 = -1. Net charge: +1+0+(−1)+(−1)=−1+1 + 0 + (-1) + (-1) = -1. Three resonance structures exist.

Answer

[NO3]− with 3 resonance structures; N has formal charge +1[\text{NO}_3]^-\text{ with 3 resonance structures; N has formal charge +1}
Resonance structures show that the actual electron distribution is an average of all valid Lewis structures. In nitrate, all three N–O bonds are equivalent with a bond order of 43\frac{4}{3}.

About Lewis Structure

A two-dimensional diagram that represents the arrangement of valence electrons around atoms in a molecule, showing bonding pairs as lines between atoms and non-bonding (lone).

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More Lewis Structure Examples

Example 1 easy

Draw the Lewis structure for water ([formula]).

Example 2 medium

Draw the Lewis structure for carbon dioxide ([formula]).

Example 4 medium

Draw the Lewis structure for ammonia ([formula]), and state how many lone pairs are on the nitrogen

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