Weakest reducing agent (among alkali metals) in aqueous solution is

A) Hydration Enthalpy….Li⁺>Na⁺>K⁺>Rb⁺>Cs⁺

B) ${\mathrm{E}}_{{\mathrm{M}}^{+}/\mathrm{M}}^{°}$ values are negative.

Most negative for Li and least negative for Na.

${\mathrm{E}}_{{\mathrm{Li}}^{+}/\mathrm{Li}}^{°}\left(\mathrm{most} \mathrm{negative}\right)<{\mathrm{E}}_{{\mathrm{Cs}}^{+}/\mathrm{Cs}}^{°}<{\mathrm{E}}_{{\mathrm{Rb}}^{+}/\mathrm{Rb}}^{°}<{\mathrm{E}}_{{\mathrm{K}}^{+}/\mathrm{K}}^{°}<{\mathrm{E}}_{{\mathrm{Na}}^{+}/\mathrm{Na}}^{°}\left(\mathrm{least} \mathrm{negative}\right)$

Best reducing agent is Lithium, best oxidant is Na⁺;