The following Lewis diagram represents the valence electron configuration of a main-group element. This element is in group 2A According to the octet rule, this element would be expected to form a(n) with a charge of cation anion If X is in period 4, the ion formed has the same electron configuration as the noble gas The symbol for the ion is

The symbol of the ion formed is

Explanation:

An ion is formed when a neutral atom looses or gains electrons.

Electronic configuration is defined as the representation of electrons around the nucleus of an atom.

Number of electrons in an atom is determined by the atomic number of that atom.

The element present in Group 2-A and in period 4 is Calcium (Ca)

Electronic configuration of Ca atom:  

This atom will loose 2 electrons to attain stable electronic configuration similar to Argon element (noble gas)

The electronic configration of

Hence, the symbol of the ion formed is

a electronegativity decreases beacuse the size of nucleus is bigger.