Activation energy...?

Question

it's negative for endothermic reactions and positive for exothermic reactions, correct? :)

Answer 1

No.  You are thinking of enthalpy, not activation energy.  Activation energy must always be "added", so to speak, in order to get a reaction to occur.

Enthalpy, delta H, may be positive or negative.  A positive DH means that the reaction is endothermic, the products are at a higher energy than the reactants.  When DH is negative we have an exothermic reaction.  Energy is given off as the reactants form the products, which are lower in energy.