So what can a 50kt device do?
3X what a Hiroshima device can do.
Wipe out one Israeli city, and a whole bunch of Iranian cities.
Surround it with a cobalt jacket and set it off where prevailing winds will carry fallout over most of central Israel. You don't need to kill that many people. You just have to make the area so unhealthy that rational people don't want to live there any more.
It won't matter if the Palestinians can't live there either. The objective all along was to displace the Jews, rather than settle the Palestinians.
“So what can a 50kt device do?”
If they manage to deliver it perfectly (i.e., location and altitude), it can pretty much take out a medium-sized city. So, no, one will not take out Israel (assuming they can handle the associated EMP, but that’s a separate topic), but half a dozen, yes. A single 10 MT blast would pretty much wipe out the northern half of Israel.
These weapons aren’t toys, but it looks like Israel takes its defense quite seriously.
You can play around with some templates, targets and various devices here:
http://www.nucleardarkness.org/nuclear/nuclearexplosionsimulator/
Take out ALL NYC, or LA, Or DC. Plus a little. Probably about ten miles in circumference. Then lots of crap in the air.
Use your imagination. Picture a ton of TNT on a football field and expect it to absolutely destroy everything on the field - every blade of grass and make it so you never knew the bleachers were there.
Now, picture 50,000 football fields all bunched together. How far do they stretch in all directions?