The hydroxide ion (OH-) consists of one oxygen atom (O) and one hydrogen atom (H). To determine the formal charges on these atoms in the hydroxide ion, we need to compare the number of valence electrons each atom has with the number of electrons it “owns” in the ion.
Oxygen (O) has six valence electrons (assuming neutral state), and hydrogen (H) has one valence electron. In the hydroxide ion (OH-), oxygen forms a single bond with hydrogen, resulting in the following arrangement:
O
||
H
In this structure, oxygen has seven electrons (six valence electrons + one from the hydrogen atom) and hydrogen has two electrons (its one valence electron + one from the oxygen atom).
Now, let’s calculate the formal charges:
Formal charge on oxygen (O) = Number of valence electrons – Number of lone pair electrons – Number of shared electrons Formal charge on hydrogen (H) = Number of valence electrons – Number of lone pair electrons – Number of shared electrons
For oxygen (O): Formal charge = 6 – 4 – 2 = 0
For hydrogen (H): Formal charge = 1 – 0 – 2 = -1
Therefore, the formal charge on oxygen (O) in the hydroxide ion is 0, and the formal charge on hydrogen (H) is -1.