Explain the deviation in the ionization enthalpy of some elements from the general trend using the provided graph.

(N/A) The general trend in a period is that the first ionization enthalpy increases from left to right due to an increase in effective nuclear charge and a decrease in atomic radius.
However,there are deviations in this trend:
$1$. $Be$ $(1s^2 2s^2)$ has a higher ionization enthalpy than $B$ $(1s^2 2s^2 2p^1)$. This is because $Be$ has a fully filled $2s$ orbital,which is more stable and requires more energy to remove an electron compared to the $2p$ electron in $B$.
$2$. $N$ $(1s^2 2s^2 2p^3)$ has a higher ionization enthalpy than $O$ $(1s^2 2s^2 2p^4)$. This is because $N$ has a half-filled $2p$ subshell,which provides extra stability. In $O$,the removal of an electron leads to a more stable half-filled $p$-orbital configuration,making it easier to remove an electron compared to $N$.