The correct option is STRONTIUM.
Strontium is a group 2 element, that means it has two electrons in its outermost shell. This element will prefer to lose these two electrons in its outermost shell in order to attain the octet form, therefore, it will form electrovalent bond with non metals which it can donate two electrons to.
Endothermic reactions are reactions that require heat in the course of the process. The heat of reaction in this case is positive which means the energy of the products is greater than the energy of the reactants. In this case, the answer to this problem would have to be <span>1. must be greater than the required ΔH </span>
