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The first ionization energy for $Be$ is 899 kJ/mol, while $B$ has a first ionization energy of 800 kJ/mol. This data does not fit the usual trend of ionization energies.
Which of the following is the BEST statement to justify the data?
The valence electrons in $Be$ are removed from a full 2s subshell with less shielding compared to a not full 2p subshell in $B$.
$Be$ has valence electrons in the 2s subshell, which is much closer to the nucleus and less difficult to remove than the 2p valence electrons in $B$.
Moving left to right on the periodic table, there are more protons in the nucleus attracting the electrons, thus making it more difficult to remove electrons.
$B$ has more electrons than $Be$, increasing the electron-electron repulsions and lowering the ionization energy for $B$.