{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Chapter8 - 8 Understanding Lewis Structures Triple Bonds...

Info icon This preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
8 Understanding Lewis Structures Triple Bonds Students sometimes get the idea that triple bonds are not desirable. That is not true. Many molecules have triple bonds. Look at these two examples. HC CH (0) (0) The only way to make the carbon have an octet of electrons is to have a triple bond. The formal charges (in parenthesis) are both zero. This is a very happy molecule. Many of you are familiar with this molecule. C 2 H 2 is acetylene and is used in gas torches for cutting metal and welding. Carbon monoxide has two possible Lewis structures.
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
2 Chapter 8 Understanding Lewis Structures C O (-1) (+1) C O (0) (0) A B Structure B has good formal charges but the carbon atom does not have an octet. Structure A has a carbon with an octet but bad formal charges. Note the +1 formal charge on the very electronegative oxygen atom in structure A . (Bad, Bad, Bad!!) If carbon were allowed to violate the octet rule ( like B or Be ) then structure B might be preferred. However, carbon is not allowed to violate the octet rule. The octet rule is more important in this case than the formal charges. Structure A with the triple bond will be preferred even though the formal charges are worse. I Try to avoid positive formal charges on the most electronega- tive atom. Sometimes, however, it is necessary as in the case of CO. An Analogy of Resonance Imagine painting a picture of a fl ower using only two inks. One
Image of page 2
An Analogy of Resonance 3 is a light tone and the other dark. Suppose further that we are only alowed to use one ink at a time. With the light ink by itself we can paint most of the petals. With the dark ink we can paint the rest of the petals, the leaves and stem. But neither the light toned painting nor the dark toned painting represents the real fl ower. The real fl ower
Image of page 3

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
4 Chapter 8 Understanding Lewis Structures is a hybrid or mixture of the two top paintings. The reason
Image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern