This element’s liquid form is used as a scintillation target to look for WIMPs in the LZ experiment. The EXO experiment is searching (10[2])for evidence of one (-5[1])isotope of this element undergoing neutrinoless double beta decay. An (-5[1])isotope of this element is the most powerful neutron absorber known, and its buildup in reactors can lead to a namesake “poisoning” (10[1]-5[3])that contributed (10[1]-5[2])to the Chernobyl (-5[1])meltdown. (10[2])The NSTAR (10[1])and NEXT ion engines use this element as propellant. (10[1])The first (10[1])excimer lasers used dimers of this element, which is the most common gas ionized by arc lamps. (-5[1])Neil Bartlett (-5[1])reacted (10[1])this element (10[2])with platinum hexafluoride (10[1])to create the (10[1])first known noble (10[1])gas compound. (10[5]-5[1])Beta decay (10[1])of (10[1])iodine (10[1])yields, for 10 points, what noble gas with atomic number (10[1])54, (10[1])which lies below krypton? (10[2])■END■ (10[11]0[2])