Final answer:
Hydronium ions (H3O+) form in water when a water molecule accepts a hydrogen ion (H¹) from another water molecule, resulting in the creation of both hydronium and hydroxide ions.
Step-by-step explanation:
Hydronium ions form when acids are dissolved in water, and they are represented by the symbol H3O+.
In a process called self-ionization, two water molecules can react, one giving up a hydrogen ion (H¹) which is then accepted by another water molecule, forming a hydronium ion (H3O+) and a hydroxide ion (OH-). This reaction can be represented as 2H₂O → H3O+ + OH−.
The formation of the hydronium ion is due to the polar nature of water, with the oxygen atom carrying a partial negative charge due to its higher electronegativity.
The lone pair of electrons on the oxygen atom gives the hydronium ion a trigonal pyramidal geometry with a bond angle of approximately 113 degrees. It is important to note that in aqueous solutions, these hydrogen ions do not exist freely but are associated with water molecules, forming the hydronium ion.