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OH- (Hydroxyl ion) Lewis Structure, Steps of Drawing

OH- (Hydroxyl ion) Lewis Structure, Steps of Drawing

In OH- ion, there are only one oxygen atom and hydrogen atom. OH- (hydroxyl ion) lewis structure contains only a single bond between oxygen and hydrogen atom. There is a -1 charge on oxygen atom which represents overall charge of OH- ion.. There are three lone pairs on oxygen atom in lewis structure of OH- ion. Each step of drawing lewis structure of OH- ion is explained in detail in this tutorial.


OH- lewis structure

 hydroxyl ion OH- lewis structure

There is only one sigma bond between hydrogen and oxygen atoms in lewis structure of OH- ion. Also, there are three lone pairs on oxygen atom.




Steps of drawing lewis structure of OH- ion

There are several steps to draw a lewis structure. For OH- ion, we use those steps. Those steps are explained in detail in this tutorial. Basic steps of drawing lewis structures are listed below.

  1. Find total number of electrons of the valance shells of hydrogen atom and oxygen atom
  2. Total electrons pairs as lone pairs and bonds
  3. Center atom selection
  4. Mark lone pairs on atoms
  5. Mark charges on atoms if there are charges.
  6. Check the stability and minimize charges on atoms by converting lone pairs to bonds to obtain best lewis structure.

Total number of electrons of the valance shells of OH- ion

There are only two elements in OH- ion; hydrogen and oxygen. Hydrogen is a group IA element and has only one electron in its last shell (valence shell). Oxygen is a group VIA element in the periodic table and contains six electrons in its last shell. Now we know how many electrons are includes in valence shells of hydrogen and oxygen atom.


  • valence electrons given by hydrogen atoms = 1 * 1 = 1
  • valence electrons given by sulfur atom = 6*1 = 6
  • Valence electrons received due to -1 charge = 1

  • Total valence electrons = 1 + 6 + 1 = 8



Total valence electrons pairs

Total valance electrons pairs = σ bonds + π bonds + lone pairs at valence shells

Total electron pairs are determined by dividing the number total valence electrons by two. For, OH- ion, total pairs of electrons are 4 in their valence shells.



Center atom and sketch of OH- ion

To be the center atom, ability of having greater valance is important. In this case, we don't need to worry about selecting center atom because there are only two atoms. Therefore, we can easily draw the sketch of Oh- ion.

sketch of OH-

Lone pairs on atoms

So, deciding the sketch of OH- ion was simple. Now, we have to mark lone pairs on atoms.

  • There are only one bond in the above drawn sketch. Therefore, three (4-1) electron pairs are remaining to mark on atoms.
  • Usually, those remaining electron pairs should be started to mark on outside atoms (not first on center atom). But in OH-, there are only two atoms. Hydrogen atom cannot keep more than two electron in its last shell. There are already two electrons in the last shell of hydrogen atom. Therefore, we cannot mark those two electrons pairs on hydrogen atoms.
  • Therefore, then mark those three remaining electrons pairs oxygen atom.
mark lone pairs on OH- ion

Mark charges on atoms

OH- contains -1 charge. There is already -1 charge on oxygen atom and no charge on hydrogen atom in above structure.

there is a -1 charge on oxygen atom in OH- lewis structure

Check the stability and minimize charges on atoms by converting lone pairs to bonds

Because hydrogen atom cannot make double bond, we cannot convert a lone pair on oxygen atom to make a one more bond. Also, there is only -1 charge in above sketch and we don't need to reduce it because OH- contains -1 charge. Therefore, we have already got the best lewis structure for OH- ion.



Because there are three lone pairs with a -1 charge on oxygen atom, OH- behaves as a base.





Questions




How many lone pairs and bonds on oxygen atom in OH- lewis structure?

There are seven lone pairs on oxygen atom in OH- lewis structure. There is only one sigma bond between oxygen and hydrogen atom.



What are the other structures similar to OH-

HS- is very similar to OH- considering number of lone pairs on sulfur atom and oxygen atom in HS- and OH- respectively.















Lewis Structures of Molecules



Chemical Reactions