Crystal structures with ions must have a. a 2+ charge b. a negative charge c. electrical neutrality d. a positive charge

Crystal structures with ions must have c. electrical neutrality.
There are positive cations and negative anions in crystal structures, there can be more cations or anions, but summ of positive and negative charges in crystal structures are equal.
For example BaCl₂, barium cation is 2+ and chlorine anions are 1- (2-).

The answers is a nuclear changes

No. an alpha particle is a pair of protons and a pair of neutrons, i.e. a helium