[5] Going from the bottom to the top of the table the metals: There is no unique and fully consistent way to define the reactivity series, but it is common to use the three types of reaction listed below, many of which can be performed in a high-school laboratory (at least as demonstrations).
(In any case, the typical oxidation states for the most accessible seventh-period elements thorium and uranium are too high to allow a direct comparison.
Standard electrode potentials offer a quantitative measure of the power of a reducing agent, rather than the qualitative considerations of other reactive series.
Even with this proviso, the electrode potentials of lithium and sodium – and hence their positions in the electrochemical series – appear anomalous.
Li > Cs > Rb > K > Ba > Sr > Ca > Na > La > Y > Mg > Ce > Sc > Be > Al > Ti > Mn > V > Cr > Zn > Ga > Fe > Cd > In > Tl > Co > Ni > Sn > Pb > (H) > Sb > Bi > Cu > Po > Ru > Rh > Ag > Hg > Pd > Ir > Pt > Au