The hydroxide ion is OH-. The hydroxyl radical is OH. How many valence electrons has the hydroxide ion? Draw its Lewis dot structure. How many valence electrons has the hydroxyl radical? Draw its Lewis dot structure.
The Correct Answer and Explanation is:
Answer:
- Hydroxide ion (OH⁻):
- Valence electrons: 8
- Lewis structure:
H–O⁻ (with three lone pairs on oxygen)
- Hydroxyl radical (OH):
- Valence electrons: 7
- Lewis structure:
H–O• (with two lone pairs on oxygen and one unpaired electron)
Explanation):
The hydroxide ion (OH⁻) and the hydroxyl radical (OH) both consist of one oxygen atom bonded to one hydrogen atom. The difference lies in the overall charge and number of electrons.
For OH⁻ (hydroxide ion):
- Oxygen has 6 valence electrons, and hydrogen has 1.
- The negative charge means one extra electron is added, making a total of 6 + 1 + 1 = 8 valence electrons.
- In its Lewis structure, the oxygen forms a single bond with hydrogen (sharing 2 electrons), and the remaining 6 electrons are arranged as three lone pairs on oxygen.
- The oxygen also carries a formal negative charge due to having one more electron than it has protons.
For OH (hydroxyl radical):
- It consists of oxygen (6 valence electrons) and hydrogen (1 valence electron), totaling 7 valence electrons.
- There is no extra electron added since this is a neutral species.
- The Lewis structure shows a single bond between O and H, two lone pairs on oxygen, and one unpaired electron also on oxygen.
- The presence of this unpaired electron makes OH a radical, which is a highly reactive species.
The unpaired electron in OH is responsible for its radical nature, making it highly reactive in biological and chemical systems. By contrast, the extra electron in OH⁻ makes it more stable and gives it basic properties in aqueous solutions. Both species play important roles in chemistry and biology, especially in redox reactions and acid–base chemistry.
