Answer is: zirconium-98.
Nuclear reaction: ²³⁵U + n°→ ¹³⁵Te + ⁹⁸Zr + 3n°.
Atomic number of uranium is 92, atomic number of zirconium (Zr) is 40 and atomic number of tellurium (Te) is 52, 92 = 40 + 52.
Uranium has atomic mass 235, zirconium has 98 and tellurium has 135:
235 + 1 = 135 + 98 +3, 236 = 236.
n° is neutron.
Symbol for atomic number is Z and for atomic mass is A.
