A proton bonds to the oxygen atom of a solvent water to give a _______________________ hydronium ion.
Show answer & explanation
Correct answer: B
Explanation
The correct answer is Option 2 i.e. trigonal pyramidal.
When a proton bonds to the oxygen atom in a water molecule, it forms the hydronium ion (H₃O⁺). Although the oxygen atom in H₃O⁺ is sp³ hybridized (which gives a tetrahedral electron pair geometry), the presence of a lone pair results in a molecular geometry that is trigonal pyramidal. This shape is due to the three bonding pairs of electrons around the oxygen and one lone pair that is not visible in the molecular shape.
Why Not the Other Options?
- Square pyramid: This geometry involves five groups of electrons arranged around a central atom, which is not the case in H₃O⁺.
- Tetrahedral: While the electron pair geometry is tetrahedral, the actual molecular shape (considering only the positions of the atoms) is trigonal pyramidal because of the lone pair on oxygen.
- Square planar: This geometry is typical for certain complexes with four ligands arranged in a plane, which does not describe the structure of the hydronium ion.
Thus, the correct answer is trigonal pyramidal.