To determine the molecule polarity of the [tex]$H_3O^+$[/tex] (hydronium ion), we need to consider its molecular geometry and the difference in electronegativity between its constituent atoms.
1. Molecular Geometry:
The [tex]$H_3O^+$[/tex] ion has a trigonal pyramidal shape. This shape occurs because it has three hydrogen atoms bonded to an oxygen atom, and there is one lone pair of electrons on the oxygen. The lone pair causes a repulsion that pushes the hydrogen atoms slightly closer together, resulting in a pyramidal structure.
2. Electronegativity Values:
- The electronegativity of oxygen is 3.44.
- The electronegativity of hydrogen is 2.20.
3. Electronegativity Difference:
The difference in electronegativity between oxygen and hydrogen can be calculated as follows:
[tex]\[
\Delta \text{EN} = \text{Electronegativity}_{\text{Oxygen}} - \text{Electronegativity}_{\text{Hydrogen}} = 3.44 - 2.20 = 1.24
\][/tex]
This difference indicates that the bonds between the oxygen and hydrogen atoms are polar covalent bonds, as the value is significantly greater than zero.
4. Molecular Dipole Moment:
Because the bonds are polar and due to the asymmetrical shape of the molecule (trigonal pyramidal), the dipoles do not cancel each other out. The lone pair of electrons on the oxygen atom enhances the net dipole moment.
5. Conclusion:
Due to the trigonal pyramidal shape and the substantial electronegativity difference between oxygen and hydrogen, the [tex]$H_3O^+$[/tex] molecule has a net dipole moment and is therefore polar.
So, the [tex]$H_3O^+$[/tex] molecule is polar, owing to its geometry and the difference in electronegativity between the oxygen and hydrogen atoms.
