It's been 40 years since I did any real chemistry and I'm trying to refresh my understanding of reactive metals. I'm trying to understand how to approach a question such as "What happens if you mix solutions of Sodium Hydroxide and Copper Sulfate". I know the result is Copper Hydroxide and Sodium Sulfate. I know Sodium is more reactive than copper but why is Sodium more reactive with the Sulfate than with the Hydroxide? I vaguely remember you need to look at the number of electrons in the outer shell and work out which reaction produces the fullest shell? Is that on the right lines?