3.7: Electron Pushing Arrows

Chem 1201 · LibreTexts

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    From LibreTexts, under CC BY-NC-SA 4.0, as the source states it; its equations are written in TeX, which the PDF shows typeset. This page at LibreTexts.

    Learning Objectives

    • To understand the use of electron pushing arrows to represent resonance.

    Illustrating the relationship between resonance structures

    To help illustrate the relationship between resonance structures, a special type of notation is used. A curved arrow, flowing from the source of electrons to their destination, illustrates this formalization of electron pushing.

    Consider the example of ozone. Two resonance structures are possible. The first resonance structure can be used to produce the second structure by conducting the following steps:

    1. A lone pair of electrons on the right-most atom are pushed into the region between the central and right-most oxygen atoms, forming a double bond.
    2. The central oxygen atom would now exceed the octet rule, so a shared electron pair is pushed out from the region between the central and left-most atoms onto the left most oxygen atom.

    Note that the electrons flow simultaneously, so both electron pushing arrows are drawn at the same time.

    electron pushing in ozone.png

    Exercise 3.7.1: Nitrate Ion

    Sketch a resonance structure for the nitrate ion (NO3−), and then use electron pushing to generate two additional resonance structures for this ion.

    Click to Check Answer
    electron pushing in nitrate ion.png

    Summary

    Electron pushing arrows provide a visual representation of how one resonance structure is associated to another, and can be used to help predict other possible resonance structures.

    3.7: Electron Pushing Arrows is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by LibreTexts.