Question

Uranium-235 undergoes nuclear fission as shown in the diagram below.

A small gray ball labeled n impacts a large mass of red and gray balls labeled superscript 235 subscript 92 upper U. The impact gives off a smaller mass of balls labeled superscript 139 subscript 56 upper B a, a starburst labeled 200 megavolts, which in turn gives off 2 balls labeled n; and another smaller mass of balls labeled X.

Which element does X represent?
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Answer 1

X is krypton-95 (Kr).

Reason: conserve mass and charge. Neutron + U-235 = A=236, Z=92. Subtract Ba-139 (A=139, Z=56) and two neutrons (2×A=1) gives A = 236−139−2 = 95; Z = 92−56 = 36 → element with Z=36 is krypton.