Final answer:
The atomic structure of the H3O+ ion (hydronium ion) is described by three hydrogen atoms bonded to a central oxygen atom with a lone pair, creating a trigonal pyramidal shape according to VSEPR theory.
Step-by-step explanation:
The question is asking to describe the atomic structure of the H3O+ ion, also known as the hydronium ion. The hydronium ion forms when acids are dissolved in water, and its structure can be described using the VSEPR theory. For the hydronium ion, we have three hydrogen atoms bonded to a central oxygen atom, with the oxygen also bearing a lone pair of electrons.
Therefore, in terms of VSEPR notation, we classify it as an AX3E molecule, where 'A' denotes the central atom (oxygen), 'X' represents the bonded atoms (hydrogen), and 'E' signifies the lone pairs on the central atom. The predicted electron-pair geometry is tetrahedral, and due to the presence of one lone pair, the molecular geometry is trigonal pyramidal.