Chemistry · Classification of Elements and Periodicity in Properties

The first ionization enthalpy of boron (\( Z = 5 \)) is slightly less than that of beryllium (\( Z = 4 \)). Which formula/expression correctly reflects the electronic configuration difference responsible for this anomaly during ionization?

1. \( \text{B}: 1s^2 2s^2 2p^1 \rightarrow e^{-} \text{ removed from } 2s \text{ vs. Be}: 1s^2 2p^2 \rightarrow e^{-} \text{ removed from } 2p \)
2. \( \text{B}: 1s^2 2s^2 2p^1 \rightarrow e^{-} \text{ removed from } 2p \text{ vs. Be}: 1s^2 2s^2 \rightarrow e^{-} \text{ removed from } 2s \)
3. \( \text{B}: 1s^2 2p^3 \rightarrow e^{-} \text{ removed from } 2p \text{ vs. Be}: 1s^2 2s^2 \rightarrow e^{-} \text{ removed from } 2s \)
4. \( \text{B}: 1s^2 2s^1 2p^2 \rightarrow e^{-} \text{ removed from } 2p \text{ vs. Be}: 1s^2 2s^2 \rightarrow e^{-} \text{ removed from } 2p \)