Ionization energy of Boron is smaller than Beryllium even though effective nuclear charge is higher?

The electronic configurations of Boron and Beryllium are (₅B=1S²,2S²,2p¹) and (₄Be =1S²,2S²).

In Boron the outermost electron is present in the 2p orbital (low penetration power) and is less strongly bound than the electron present in a 2S orbital of Beryllium (Have more penetration power), which will has a higher Zeff. It is easier to ionize the Boron atom.

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