yeah an atom bomb is the most primitive nuclear device - simpler than a nuclear reactor and simpler than a hydrogen bomb 

if USSR could build a hydrogen bomb WAY back in the day and Florida can run nuclear reactors then i am sure Israel could easily build an atom bomb considering they have a history of stealing US military secrets and some of the most advanced Tech corporations like Intel have offices in Israel ...

it's possible that they don't have nukes but like you said they could easily get them if they wanted