Uningenia
Start studyingStart
Chemical BondingHard

Lewis structures and formal charge

Draw the Lewis structure of nitrate ion NO₃⁻. Calculate the formal charge of each atom and determine the most stable resonance structure.
Valence: N=5, O=6, charge -1 = +1 e⁻.
Given data
total e⁻: 5 + 3×6 + 1 = 24 e⁻pairs: 12 pairs
Review the theory: Legami Chimici
Steps
0 / 3
  1. Assign N central bonded to 3 O (1 double, 2 single). Total valence e⁻?
  2. In the structure with one N=O double bond, calculate the formal charge of the double-bonded O (FC = 6 - 4 - 4/2).
  3. Calculate formal charge of nitrogen in the same structure (FC = 5 - 0 - 8/2).
Full worked solution
  1. Assign N central bonded to 3 O (1 double, 2 single). Total valence e⁻?
    5+3⋅6+15 + 3\cdot6 + 1
    5+3⋅6+1=5+18+1=24=24 e−5 + 3\cdot6 + 1 = 5 + 18 + 1 = 24 = \mathbf{24\,e^-}. Charge -1 adds 1 e⁻.
  2. In the structure with one N=O double bond, calculate the formal charge of the double-bonded O (FC = 6 - 4 - 4/2).
    6−4−426 - 4 - \frac{4}{2}
    6−4−42=6−4−2=0=06 - 4 - \frac{4}{2} = 6 - 4 - 2 = 0 = \mathbf{0}. Zero formal charge.
  3. Calculate formal charge of nitrogen in the same structure (FC = 5 - 0 - 8/2).
    5−0−825 - 0 - \frac{8}{2}
    5−0−82=5−0−4=1=+15 - 0 - \frac{8}{2} = 5 - 0 - 4 = 1 = \mathbf{+1}. Positive formal charge.
Result:The most stable structure has formal charge -1 on terminal O and +1 on central N.
TheoryLegami ChimiciFormula sheetChemistry

Similar exercises