I cant entirely tell for now but an article on rodioactivity should solve the problem
Answer:
2-
Explanation:
For an element to be stable, it must follow the octet rule: an atom will gain, lose or share electrons until its valence shell is complete with 8 electrons.
An element with the valence electron configuration ns²np⁴ has 6 (2+4) electrons in its valence shell. Thus, in order to fulfill the octet, it will gain 2 electrons. As a consequence, it will form an anion with charge 2-.
Alkali metals have the lowest electronegativities, while halogens have the highest.
Because matter cannot be created or destroyed
