Question

explain the difference in first ionization energy between lithium and beryllium

Answer 1

Ist IE of Be will be greater than Li as Be has ful filled electronic configuration so more energy will be needed to remove the electron.

Answer 2

In the first ionization enthalpy in case of Li, the electron is removed from the 2s^1 orbital whereas in case of Be the electron is removed from 2s^2 orbital hence more energy is required to remove the electron in case of Be because the 2s orbital is completely filled whereas in case of Li the electron has to be removed from the half filled 2s orbital. So Li readily gives away 1 electron in order to obtain a stable electronic configuration.
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