The question of whether park chairs exist that can detect tennessine, element 117 on the periodic table, ventures directly from science fiction into the realm of speculative science. The short and direct answer is no; there are currently no park chairs with this capability. Tennnessine is an incredibly rare, synthetic element. It is not found in nature and has only ever been produced in minute quantities within highly specialized particle accelerators, with atoms lasting for mere milliseconds. The technology required to detect such an unstable, man-made element is monumental, involving equipment like mass spectrometers that are far too large, complex, and expensive to be integrated into public furniture.

However, the concept opens a fascinating discussion about the future of smart urban infrastructure. We already see "smart benches" equipped with solar panels, USB chargers, and environmental sensors that monitor air quality or noise levels. Theoretically, one could imagine a future where public furniture is embedded with sophisticated sensors for scientific or safety monitoring. But detecting a specific, transient superheavy element like tennessine in an open-air park environment presents insurmountable challenges with our current understanding of physics and engineering. The primary hurdle is the sheer impossibility of tennessine being present outdoors. Furthermore, the energy and computational power needed for such precise atomic-level detection are beyond the scope of what a park chair could feasibly contain.

Therefore, while the idea is a stimulating thought experiment highlighting the rapid advancement of sensor technology, it remains firmly in the domain of imagination. For now, park chairs are best suited for providing rest and relaxation, not for pioneering nuclear physics research. Any claim of a chair detecting tennessine would be purely fictional.