Molecular shape for no3-

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molecular shape for no3-

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What is the molecular shape for NO₃⁻?

Answer: To determine the molecular shape of the nitrate ion (\text{NO}_3^-), we need to follow a systematic process based on the VSEPR (Valence Shell Electron Pair Repulsion) theory. Below are the step-by-step details:

1. Determine the Lewis Structure:

  • Count the Total Number of Valence Electrons:

    • Nitrogen (N) has 5 valence electrons.
    • Each Oxygen (O) has 6 valence electrons.
    • Since there are three oxygens, that adds up to (6 \times 3 = 18) valence electrons.
    • Additionally, the negative charge adds 1 more electron.
    • Total valence electrons: (5 + 18 + 1 = 24).

  • Draw the Initial Lewis Structure:

    • Place Nitrogen in the center as the least electronegative element.

    • Connect each Oxygen to Nitrogen with a single bond.

    • Distribute the remaining electrons to satisfy the octet rule for each atom:

      \begin{array}{c} O \\ || \\ N - O \\ || \\ O \\ \end{array}

      Each O-N bond contains 2 electrons (single bond), giving 6 valence electrons used in bonds. There are 24 - 6 = 18 valence electrons left to distribute. Each O gets 6 electrons as lone pairs to complete their octet and the extra electron completes the octet for the central N making:

      \text{Nitrate ion Lewis structure}: \quad [O=N-O^-] \quad \text{(with resonance structures)}

2. Determine the Electron Domain Geometry:

  • Electron Domains:

    • Each single bond counts as one electron domain.
    • There are three regions of electron density (one for each bond) around the central nitrogen atom.
    • For NO₃⁻, there are no lone pairs on the nitrogen atom.

  • Electron Domain Geometry:

    • With three regions of electron density, the electron domain geometry is trigonal planar.

3. Determine the Molecular Geometry (Shape):

  • Molecular Geometry:
    • Since there are no lone pairs on the central nitrogen, the electron domain geometry and the molecular geometry are the same.
    • Therefore, the molecular shape is also trigonal planar.

4. Bond Angles:

  • In a trigonal planar geometry, the bond angles are approximately 120 degrees.

Conclusion:
The molecular shape of the nitrate ion (\text{NO}_3^-) is trigonal planar with bond angles of approximately 120 degrees. The structure is symmetric, and resonance delocalizes the negative charge across the three oxygen atoms, contributing to the stability of the ion.

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