[saman_Z]

please throw some light on how high energies of atomisation and hydration make beryllium a better reducing agent(though it has less negative electrode reduction value).

[aldoxime_amine]

Entropy change during formation of Be²⁺_aq from Be_aq can be assumed to be 0, so that

During Be_aq  Be²⁺_aq +2e^-,

E= :delta: H_sublimation +  :delta: H_{ionization 1} +  :delta: H_{ionization 2} +  :delta: H_hydration

Also, your statement is contradictory:
"better reducing agent(though it has less negative electrode reduction value)."