The question "Are there park chairs that detect nihonium?" sounds like something from a science fiction novel. The direct and simple answer is no; as of today, no such park benches exist for public or scientific use. Nihonium is a synthetic, highly radioactive element with an atomic number of 113. It is incredibly rare, unstable, and decays in a fraction of a second. Its production requires powerful particle accelerators and happens on a scale of atoms, not in quantities that could be "detected" by a sensor in a public park.

However, let's explore this fascinating hypothetical scenario. What would it take to create such a device? A nihonium-detecting park chair would need technology far beyond our current capabilities. It would require a built-in particle accelerator or a supremely sensitive radiation spectrometer capable of identifying the unique decay signature of a handful of atoms. The chair would essentially be a massive, powerful, and prohibitively expensive scientific instrument, making its installation in a public park highly impractical and potentially hazardous due to radiation.

The concept, while scientifically implausible, opens a discussion about the future of public infrastructure. Could we one day have benches that monitor air quality, detect specific pollutants, or analyze environmental DNA? This idea pushes the boundary of imagination, merging everyday objects with advanced scientific instrumentation. It highlights a future where public spaces are not just for rest but are interactive hubs for environmental and scientific monitoring. So, while a nihonium-detecting chair remains firmly in the realm of fantasy, it inspires innovative thinking about the smart cities of tomorrow.