Question

which reaction represents fission?
\ce{_{88}^{226}ra -> _{86}^{222}rn + _{2}^{4}he}
\ce{_{92}^{235}u + _{0}^{1}n -> _{35}^{89}br + _{57}^{144}la + 3_{0}^{1}n}
\ce{_{7}^{14}n + _{0}^{1}n -> _{6}^{14}c + _{1}^{1}h}
\ce{_{1}^{2}h + _{1}^{2}h -> _{2}^{4}he}

Explanation:

Nuclear fission is defined as a heavy nucleus splitting into smaller nuclei, often with neutron absorption and release of additional neutrons.

1. The yellow card shows alpha decay (a nucleus emits a helium nucleus).
2. The blue card shows a heavy uranium nucleus absorbing a neutron, then splitting into smaller bromine and lanthanum nuclei, plus extra neutrons—this matches fission.
3. The orange card shows neutron capture and transmutation, not splitting into large fragments.
4. The green card shows nuclear fusion (light nuclei combining into a heavier one).

Answer:

$\boldsymbol{_{92}^{235}U + _{0}^{1}n
ightarrow _{35}^{87}Br + _{57}^{146}La + 3_{0}^{1}n}$ (the reaction on the blue card)