Chemistry

Question

Draw the best lewis structure for the free radical, no2. what is the formal charge on the n?

1 Answer

  • Answer:

    The Lewis Structure of NO2 is below in the image.

    And the Formal charge of Nitrogen is +1

    Explanation:

    1. In order to make a Lewis Structure, first we check the valence electron of Nitrogen and Oxygen.

    Valence Electron Nitrogen: 5

    Valence Electron Oxygen: 6 x 2 atoms= 12

    Valence Electron total : 17

         2. We have 17 valence electron in order to make our bonds. Now we put the Nitrogen in the middle and the Oxygen on both sides and then we draw the principal bond between the Nitrogen and Oxygens

    O=N-O

    For now, we have only used 6 valence electrons when drawing the 3 covalent bonds.

              3. Remember that 17 Valence Electron were available, now we substract 6, and we have 11 Valence electrons to distribute among the elements always fulfilling the octet rule, these 11 electrons are called non-binding electrons.

    We start by allocating electrons to the elements that are more electronegative like the Oxygen, until we fulfill the octet rule. The Oxygen with double bond will have 2 pairs of non-binding electrons, and the other oxygen with 1 bond, will have 3 pairs of non-binding electrons.  For a total of 10 electrons used out of 11.

                  4. Now we have only 1 Valence electron that will be assigned to the Nitrogen, as we can see in the image below.

    The Formal Charge in the molecule is easy to find. It´s the difference between the valence electrons (VE) and the electrons assigned in the Lewis structure (LE).

    First Oxygen: VE : 6    LE: 6.  Formal Charge is 6-6= 0

    Nitrogen: VE: 5    LE: 4.           Formal Charge is 5-4= +1

    Second Oxygen: VE: 6   LE: 7 Formal Charge is 6-7= -1

    Keep in mind that a molecule like NO2 will start to resonate, that means that some electrons in molecule start to move trying to reach the octet rule, as you can see in the second image below

       

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