Trends of electron affinity

The trend in electron affinity is to increase negatively across a group.


Does this mean noble gases' electronegativity is more negative than halogens?


Noble gases should have a positive electron affinity as adding an electron would make it unstable and thus will not happen.


But for halogens the attraction for that one electron to fill up the $\mathrm{p}$ subshell is very strong.


But given the theory that electron affinity increases negatively across the period, does this theory make an exception for noble gases?


Next, what about $\ce{Be}$ and $\ce{Mg}$? Their electron affinities are not negative.




Not exceptions, but see, theories say that going $L→R$ electron affinity increases up to halogens.


For the noble gases, $\Delta\_\mathrm{eg}H$ is positive (energy required). While electron affinity is $0$. Which implies no tendency to lose electrons.


For $\ce{Be}$, the small size and nuclear charge are responsible, which is related to $\ce{Mg}$ due to a diagonal relationship.


 0