Question

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

Explanation:

Transition metals often form multiple positively - charged ions. Nickel is a transition metal. Sodium, barium, and magnesium are main - group metals with more predictable ion charges. Sodium usually forms a +1 ion, barium a +2 ion, and magnesium a +2 ion. Nickel can form Ni²⁺ and Ni³⁺ ions.

Answer:

nickel (Ni)