Lewis Structures: Rules & Simple Molecules
Draw the Lewis structures for
hint
When drawing Lewis structures:
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Examples: HF, NH₃, and N₂
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Lewis structures: FORMAL CHARGES, IONs, & Resonance
Draw Lewis structures for the following compounds.
hint
Remember that a cation has lost electrons, so deduct the appropriate number of electrons from the total number of valence electrons available. In contrast, anions have gained electrons, so add the appropriate number of electrons to the total number of valence electrons available. We should always assign formal charges to atoms in a Lewis structures. To calculate the formal charge on an atom: \[ \text{FC} = \text{# valence e}^- - \text{# of lone pair e}^- - \frac{\text{# bonding e}^-}{2} \] The sum of all the formal charges is always equal to the total charge of the ion. Consider the nitrite ion: NO₂⁻.
SOLUTION 1
solution 2
Typically, you can determine the bond order (BO) from the type of bond:
However, a molecule that exhibits resonance is better thought of as an average structure. In other words, NO₂⁻ does not exist as neither the left resonance form nor the right resonance form. Instead, NO₂⁻ exists as an average (or hybrid) of the two resonance structures. As such, the bond order for the NO bond is neither 1 (single bond) or 2 (double bond), but 1.5. |
Example 1: Ozone (O₃)
Example 2: Carbonate (CO₃²⁻)
Example 3: Carbon Dioxide (CO₂)
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