Question

What atom in the hydronium ion, \(\mathrm{H}_{3} \mathrm{O}^{*}\), bears the positive charge?

Short answer

The positive charge in the hydronium ion is primarily on the added hydrogen atom.

Step-by-step solution

Understand the Structure

The hydronium ion, \( \mathrm{H}_3\mathrm{O}^+ \), consists of an oxygen atom bonded to three hydrogen atoms. It is derived from a water molecule (\( \mathrm{H}_2\mathrm{O} \)) by the addition of a proton (a hydrogen ion, \( \mathrm{H}^+ \)).

Analyze the Charge Distribution

In the hydronium ion, the extra \( \mathrm{H}^+ \) ion forms a bond with the lone pair of the oxygen atom in the water molecule. The result is that the positive charge is distributed over the ion, but primarily associated with the hydrogen atoms due to the addition of the proton.

Determine Charge Location

Even though the positive charge is shared over the entire hydronium ion, it is primarily carried by the added hydrogen atom. This is because the addition of a proton (\( \mathrm{H}^+ \)) changes the balance of electrons around the oxygen atom, contributing to the positive charge of the complex.

Key concepts

Oxygen Atom

The oxygen atom in the hydronium ion, \( \mathrm{H}_3\mathrm{O}^+ \), plays a crucial role. In its original form as part of a water molecule \( \mathrm{H}_2\mathrm{O} \), oxygen has two lone pairs of electrons and is covalently bonded to two hydrogen atoms. Oxygen is more electronegative than hydrogen. This means it tends to attract electrons more strongly. When a proton \( \mathrm{H}^+ \) is added to water, one of the lone pairs on the oxygen atom forms a new bond with the proton. This action changes the shape and charge distribution of the molecule, leading to the formation of the hydronium ion.

Proton Addition

The formation of the hydronium ion results from the addition of a proton, which is a hydrogen ion \( \mathrm{H}^+ \). This addition is not just a simple attachment; it involves the interaction with a lone pair on the oxygen atom of a water molecule.

• The lone electron pair of oxygen forms a coordinate covalent bond with the proton.
• This transforms the existing \( \mathrm{H}_2\mathrm{O} \) molecule into \( \mathrm{H}_3\mathrm{O}^+ \).

The process is crucial because it adds a proton, increasing the acidity of the solution. The newly added hydrogen ion shares electrons with oxygen, impacting the electron balance and structural properties.

Charge Distribution

In the hydronium ion \( \mathrm{H}_3\mathrm{O}^+ \), the charge distribution is an essential concept to grasp. The sense of balance is affected by adding one proton, which changes how electrons are shared. Oxygen holds a lot of influence over this distribution through its electronegativity.

• Electrons are pulled more towards oxygen, leaving hydrogen relatively electron-deficient.
• The overall positive charge of the ion is a result, but mostly concentrated around the newly added hydrogen.

This configuration explains why the ion behaves as it does in chemical reactions and why it possesses acidic properties.

Positive Charge Location

While the hydronium ion as a whole carries a positive charge, pinpointing its exact location is key to understanding its chemical behavior. Initially, the extra hydrogen ion was positively charged before bonding, but after bonding, the charge is more dispersed.

• The major location of the positive charge is often associated with the added hydrogen atom.
• This is due to the shift in electron density towards oxygen, influenced by its stronger electronegativity.

The positive charge does not sit statically but helps the hydronium ion interact with other molecules, especially in acid-base reactions.