(b) Ionization energy generally increases from left to right across the second period element, but boron, which is to the right of beryllium, has a lower ionization energy than beryllium. Explain. Bor on has a lower Ionization energy Beryllium than be cause He D Øshell only contains one ele ce von which makes it less stable the Beryllium which has a tulis oy bital. Muh s Solution Generally in the periods from left to right Ionisation Energy increases... Because decrease in atomic radii. But Boron having less Ionisation Energy compare to Beryllium it\'s neighbour element, reason: BORON electronic configuration 1s2 2s2 2p1 Beryllium electronic configuration 1s2 2s2 Beryllium contains completely filled 2s orbital, so it gives extra stability. That is why it needs more energy to remove the electron. Where as Boron has 2p1 electron in its valence shell it can be easily removed, so it has low Ionisation Energy .