What does fissionable material mean?

Rewrite and complete the following nuclear reaction by filling in the atomic number of Ba and mass number of Kr:

${}_{92}{}^{235}\mathrm{U} +{}_0{}^1\mathrm{n} \to {}_{\_\_\_}{}^{144}\mathrm{Ba}+{}_{36}{}^{\_\_\_}\mathrm{Kr} + 3 {}_0{}^1\mathrm{n} + \mathrm{Energy}$

Complete the following equation:

${}_3{}^6\mathrm{Li} + {}_0{}^1\mathrm{n} \to {}_{-1}{}^0\mathrm{e} + {}_2{}^4\mathrm{He}+\mathrm{\_\_\_}$

Complete the following equation:

${}_{92}{}^{235}\mathrm{U} + {}_0{}^1\mathrm{n} \to {}_{56}{}^{139}\mathrm{Ba} + {}_{36}{}^{94}\mathrm{Kr}+$_____${}_0{}^1\mathrm{n}$