Question

An aqueous solution of XCl2 contains colored ions. Element X could be

Answer 1

Cl has a charge of -1 and so element X could be a transition metal. Since there are two $Cl^-$, the transition metal must have an oxidation state of  +2 to give us the neutral charge of the compound. When a transition metal forms ions it has  incompletely filled d orbitals. This orbitals can accept electrons from ligands like $Cl^-$ ions. When the electrons of the ligand and the transition metal interact repulsion occurs. This repulsion results in the splitting of d orbitals into two groups, one having a higher energy than the other. An electron in the lower energy orbital then absorbs wavelength of light from surroundings to move to a the higher energy. This energy corresponds to a certain wavelength and we see the complementary color of that absorption.  

Answer 2

Answer:

Ni

Explanation:

The question is incomplete as the options are missing. Below are the options

(1) Ba

(2) Ca

(3) Ni

(4) Bi

In the periodic table, the only group of element that has the capacity to form colored ion in solution are known as transition elements or metals. They are characterized by partially filled d-orbitals.

From the options, only Ni (Nickel) qualifies as a transition metal and thus, the only element that can exhibit colored ion in aqueous solutions.

The correct option is option (3).