Question

Which ion is most polarizing?

Answer 1

The chemical elements gain or lose electrons to attain nearest noble or inert gas configuration. Thus, the atoms become ions with negative or positive charge. The ion with positive charge is called cation, the cation with large charge and small size has a high polarizing power.

Complete answer:
Periodic table is the representation of chemical elements arranged in the increasing order of atomic numbers and arranged in the vertical columns and horizontal rows.
The vertical columns are called groups and the horizontal rows are called periods. There are seven periods and eighteen groups in the periodic table. The elements belonging to the group $13$ are called the Boron family. As the first element in the group $13$ is Boron. So, the elements in that group can be called as the elements belonging to the Boron family.
Aluminium is that element with atomic number $13$and has three electrons in its outermost shell. It loses the three electrons and becomes a positive ion i.e.., cation thus, it exists as $A{l^{ + 3}}$.
$A{l^{ + 3}}$is the cation with large charge and small size, generally cations have small size compared to a neutral atom and the negative ion i.e.. anion.
Polarising power $\alpha$ cation charge.
Thus, $A{l^{ + 3}}$ is an ion with high polarising power. The ion with large charge and small size has high polarising power. It is able to distort the anion when anion brings contact with cation.

Note:
As the outermost electrons were removed in the cation, the nucleus has the most effect on the outer shells leading to the decrease in the size of the ion. In the anion the electrons were added to the outermost shell and thus, the size will increase.