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.
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.
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.
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.
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.
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.
So, deciding the sketch of OH- ion was simple. Now, we have to mark lone pairs on atoms.
OH- contains -1 charge. There is already -1 charge on oxygen atom and no charge on hydrogen atom in above structure.
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.
There are seven lone pairs on oxygen atom in OH- lewis structure. There is only one sigma bond between oxygen and hydrogen atom.