The reactivity of an alkali metal depends on the metals ability to

             The reactivity of an alkali metal depends on the metals ability to loose an electron.

                         Alkali metals are elements present in first group of the periodic table. Following are the metals from top to bottom;

                                               Lithium

                                               Sodium

                                               Potassium

                                               Rubidium

                                               Cesium

                                               Francium

These s-block elements are considered the most reactive metals in the periodic table because they have only one electron in their valence shell and readily loose that electron to form an ionic bond with non metal. The general electronic configuration of these metals is as follow,

                                                       nS¹

Also, the reactivity of these metals increases from top to bottom in the group as the ionization energy decreases due to increase in shielding effect respectively.

the answer would be a

the potential energy of the reactants is 200j.

from the energy diagram, the energy of the product formed is 350j; this means that, this reaction is an endothermic reaction, because it absorbs energy from its environment.