Draw the Lewis structure for a hydroxide (OH^-) ion
The Correct Answer and Explanation is:
Lewis Structure of Hydroxide Ion (OH⁻)
To draw the Lewis structure for the hydroxide ion (OH⁻), follow these steps:
- Count the Total Valence Electrons:
- Oxygen (O) is in Group 16 of the periodic table, so it has 6 valence electrons.
- Hydrogen (H) is in Group 1, so it has 1 valence electron.
- The hydroxide ion has a negative charge (OH⁻), meaning there is an additional electron.
- Total valence electrons = 6 (from oxygen) + 1 (from hydrogen) + 1 (extra electron) = 8 valence electrons.
- Determine the Central Atom:
- Oxygen will be the central atom since it is more electronegative than hydrogen.
- Arrange the Atoms:
- Place oxygen in the center, with a single bond connecting it to hydrogen. This bond will use 2 electrons (1 from oxygen and 1 from hydrogen).
- Distribute the Remaining Electrons:
- After placing the single bond (2 electrons), there are 6 electrons left to be placed.
- These remaining 6 electrons will be placed as lone pairs on the oxygen atom. Oxygen will have three lone pairs, using up the remaining 6 electrons.
- Account for the Negative Charge:
- The negative charge indicates an extra electron. This extra electron is added as a lone pair on the oxygen atom.
Final Structure:
- Oxygen: It has one single bond to hydrogen, two lone pairs, and a third lone pair with an extra electron due to the negative charge.
- Hydrogen: It is bonded to oxygen with a single bond and has no lone pairs.
The Lewis structure for the hydroxide ion is:
H
|
O : :
: (lone pair)Where:
- “O” represents oxygen.
- “:” represents lone pairs of electrons on oxygen.
- “H” represents hydrogen, which is bonded to oxygen via a single bond.
Explanation:
- Oxygen has 6 valence electrons and forms a single bond with hydrogen, using 2 electrons.
- The remaining 6 electrons are placed as three lone pairs on oxygen.
- The negative charge on OH⁻ results from an extra electron, which is added to the oxygen atom.
- The Lewis structure accurately represents the bonding and lone pairs in the hydroxide ion, illustrating the ion’s overall charge and electron distribution.