Question

Would you expect that an anion would be physically closer to the oxygen or to the hydrogens of water molecules that surround it in solution?

Short answer

Based on the polar nature of water molecules and potential hydrogen bonding interactions, an anion would be physically closer to the hydrogen atoms of water molecules surrounding it in solution. This is because the anion is attracted to the partial positive charges on the hydrogen atoms, and if the anion participates in hydrogen bonding, this attraction will be even stronger.

Step-by-step solution

Analyze the structure of water molecules and hydrogen bonding

Water has a bent molecular shape with an angle of approximately 104.5° between the hydrogen-oxygen-hydrogen atoms. The oxygen atom is more electronegative than the hydrogen atoms, which results in a polar molecule with a partial negative charge on the oxygen atom and partial positive charges on the hydrogen atoms. Additionally, hydrogen bonding is a type of intermolecular force that occurs between hydrogen atoms bonded to a highly electronegative element (like oxygen) and a nearby electronegative atom with a lone pair of electrons (another oxygen atom in the case of water).

Identify the anion and its interactions with water molecules

An anion is a negatively charged ion. Since it has a negative charge, it will be attracted to the partial positive charges on the hydrogen atoms of surrounding water molecules.

Examine the influence of hydrogen bonding on anion's position

As hydrogen bonding occurs between hydrogen atoms and electronegative atoms with lone pairs of electrons, an anion with a strong affinity for hydrogen bonding (such as a halide ion like Cl- or Br-) may also participate in hydrogen bonding with water molecules. This interaction would further influence the anion to be closer to the hydrogen atoms of the water molecules.

Determine whether the anion would be closer to the oxygen or hydrogen atoms of water molecules

Based on the polar nature of water molecules and potential hydrogen bonding interactions between anions and water molecules, we can conclude that an anion would be physically closer to the hydrogen atoms of water molecules surrounding it in solution. The anion will be attracted to the partial positive charges on the hydrogen atoms, and if the anion participates in hydrogen bonding with the water molecules, it will be even more strongly attracted to the hydrogen atoms.