Which is the most reducing agent in the periodic table?

Lithium is the best reducing agent. It is true that Francium has the lowest ionization energy, but due to its large size it has a less polarizing cations, thus it is not the best reducing agent. Lithium's relatively high ionization energy is counteracted by the large amount of energy released when the unusually small, highly polarizing Li+ cation interacts with the surrounding water molecules.

Francium is further up the periodic table, so is far stronger than lithium. If you throw a gram of Francium into water, and a gram of lithium into water, the lithium will fizzle a little bit, but the Francium will explode dramatically. educing agents are all in group 1 of the periodic table, and will get stronger as you move downwards to higher atomic number. Oxidising agents are in group 17 and will get weaker as you move downwards with increasing atomic number

The mass has escaped into a gas which you can not see so the law stays true.