MadSci Network: Chemistry

Re: What is the Lewis structure of he ClO- ion and the ClO2- ion?Covalent?

Date: Mon May 24 08:46:18 1999
Posted By: Dan Berger, Faculty Chemistry/Science, Bluffton College
Area of science: Chemistry
ID: 927309391.Ch

What is the Lewis structure of the ClO- ion and the ClO2- ion?

I am a Biology teacher assigned a chemistry class and I cannot find the answer to the questions posed above. I have a pretty good idea about drawing the Lewis structures for both of these ions, but I don't know how to determine which one has a coordinate covalent bond.

Lewis structures for almost anything can be found by following a few simple rules. The structures for ClO- (hypochlorous ion) and ClO2- (clorous ion) are quite simple and are shown above, left.

Notice that these Lewis structures show all atoms with an octet. One could, I suppose, use an "expanded octet" structure for chlorous ion as well; such a structure is shown at right.

Nevertheless, the structures which preserve 8-electron octets are more valuable for determining which compound has a "coordinate" covalent bond, because such a bond is defined as one formed from electrons "belonging" to only one of the atoms. Examples of such bonds include ammonium ion (NH4+), hydronium ion (H3O+), and phosphine oxide (H3PO); in all of these, a bond is formed by donation of a pair of electrons to an electron-deficient species (H+ or O). This donation always results in the formal charge on the acceptor atom being reduced by one unit (from +1 to 0, or from 0 to -1).

You will also notice that in every case the electron donor atom is assigned a single formal positive charge for each pair of electrons donated. So the clue to finding coordinate covalent bonds within Lewis structures is to look for formal positive charges: such a charge is found in ClO2-.

For more on this, see one of my recent answers.

  Dan Berger
  Bluffton College

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