Oksóniumionin

Oksóniumionin, also known as the hydronium ion or oxonium ion, is a polyatomic ion with the chemical formula H3O+. It is formed when a Brønsted-Lowry acid donates a proton (H+) to a water molecule (H2O). This process is a fundamental part of acid-base chemistry in aqueous solutions.

In water, protons do not exist independently but are immediately hydrated. The oxonium ion represents the most stable form of a proton in water, where the proton is covalently bonded to one oxygen atom of a water molecule through a coordinate covalent bond. The positive charge is delocalized over the entire ion.

The concentration of oxonium ions in a solution is a key factor in determining the acidity of that solution. Pure water has a very low concentration of oxonium ions, and its pH is neutral (pH 7 at 25°C). As acids are added to water, the concentration of oxonium ions increases, leading to a lower pH and a more acidic solution. Conversely, bases react with oxonium ions, reducing their concentration and increasing the pH.

While H3O+ is commonly used to represent the hydrated proton, it is important to note that in reality, hydration is more extensive. Oxonium ions can associate with additional water molecules, forming species like H5O2+, H7O3+, and so on. However, H3O+ serves as a convenient and widely accepted representation for the proton in aqueous media. The term oxonium ion is also used more generally to refer to any positively charged oxygen-containing ion, such as those found in ethers or alcohols.