Answer:
zinc, Zn²⁺, zincate ion
Explanation:
Let us check with all the given examples:
a) Fluorine (F). It is the most electronegative element and thus cannot form positive ion. It will gain electron and form a negative ion (F⁻) known as Fluoride ion.
b) Zinc: it is a metal and give two electrons easily to attain noble gas configuration. Hence it will form Zincate ion (Zn⁺²).
c) Copper,: it is a metal and can form positive ion easily.
It can give either two or one electron to form
Cu⁺²: Cupric ion [More common]
Cu⁺: Cuprous ion
d) Barium : it is alkaline earth metal and will give only two electron to form dipositive ion barium ion (Ba⁺²)
