Beryllium effective nuclear charge

The observed inter-atomic distances (Table XIX) for the beryllium salts are somewhat smaller than those calculated. This indicates that there is more deformation in these crystals than in the sodium chloride type crystals, despite the smaller effective nuclear charge of the two-shell cation and points to the existence of an increased tendency to deformation... 

The increase to 900 kJ mol" in the case of the beryllium atom is due to the increase in effective nuclear charge, offset by interelectronic repulsion of the two 2s electrons. The electron most easily removed is one of the pair in the 2s orbital. In the case of the boron atom, in spite of an increase in nuclear charge there is a decrease in the first ionization energy to 799 kJ mol. This is because the electron removed is from a 2p orbital, which is higher in energy than the 2s level. 

To estimate the effective nuclear charge experienced by the 2s electrons in beryllium, we must distinguish between two different types of shielding (1) the shielding of the outermost electrons by the core electrons and (2) the shielding of the outermost electrons by each other. The key to understanding the trend in atomic radius is the difference between these two types of shielding. 

Which electrons experience a greater effective nuclear charge the valence electrons in beryllium or the valence electrons in nitrogen Why ... 

In Section 8.6, we estimated the effective nuclear charge on beryllium s valence electrons to be slightly greater than 2+. What would a similar treatment predict for the effective nuclear charge on boron s valence electrons Would you expect the effective nuclear charge to be different for boron s 2s electrons compared to its 2p electron In what way (Hint Consider the shape of the 2p orbital compared to that of the 2s orbital.)... 

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