Which metal is most likely to form more than one kind of positively charged ion? sodium (na) barium (ba) nickel (ni) magnesium (mg)

Answer : The correct option is, Nickel (Ni)

Explanation :

Sodium is the element of s-block with symbol (Na). It belongs to the group 1.

Barium is the element of s-block with symbol (Ba). It belongs to the group 2.

Magnesium is the element of s-block with symbol (Mg). It belongs to the group 2.

Nickel is the element of d-block with symbol (Ni). It belongs to the group 10.

As we know that the d-block elements are the transition element which as ability to shows variable oxidation state.

Hence, the metal most likely to form more than one kind of positively charged ion is, Nickel (Ni)