First Example

Draw the Lewis Dot Structure for (NH2)2CO

  1. Fourth step in procedure: Place 3 nonbonding pairs of electrons on each outer atom except H.

    In this example, the outer atom that gets 3 nonbonding pairs of electrons is the oxygen atom. The nitrogen atoms are technically inner atoms since they are bonded to more than one other atom.

    Remember, nonbonding pairs of electrons are represented by two dots in the Lewis Dot Structure.

    After adding in the nonbonding electrons to the outer atoms, subtract the total number of electrons added from the amount remaining in step #3. (In this example, we had 10 valence electrons left after step #3.)

    Lewis Structure


  2. Fifth step in procedure: Assign the Remaining Valence Electrons to Inner Atoms.

    The inner atoms in our example will be the two nitrogen atoms and the one carbon atom.

    A couple of things to note at this step.

    1. Add the electrons to the "outermost" inner atoms first. (That is, add the electrons to the inner atoms of highest electronegativity.)

    2. Add one pair of valence electrons to each inner atom until either:

      1. no more valence electrons remain to be assigned.

        or

      2. each inner atom has a total of eight valence electrons assigned to it.

        (If you still have valence electrons left over after this step, assign them to the inner atoms of highest electronegativity-even if it results in an atom with more than eight valence electrons.)

    Again, after adding in the nonbonding electrons to the inner atoms, subtract the total number of electrons added from the amount remaining in step #4. (In this example, we had 4 valence electrons left after step #4.) Do not add more nonbonding electrons than you have left from step #4. The total number of nonbonding electrons remaining after this step should equal zero.

    Lewis Structure

 

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