Question

On an average how many neutrons are emitted in the fission reaction of U-235?

• A. 25
• B. 13.4
• C. 2.4
• D. 40

Answer 1

The correct option is C

2.4

U-235 after absorbing a neutron becomes U-236 and then this “Unstable” isotope fission to give daughter products and in the process neutrons are emitted.

Interesting finding is that every time a U-236 fissions same daughters are not formed. The pair of daughters formed is different in each fission tough few pairs are highly probable.
We can give you some examples: ${}_{92}^{236}U{\to }_{53}^{137}I{+}_{39}^{97}Y+2n{}^{}{}_{92}^{236}U{\to }_{56}^{140}Ba{+}_{36}^{94}Kr+2n$
Here in these examples we have two neutrons there might be such fragments formed that 3 neutrons are emitted.
$Averageno.ofneutrons=\frac{Totalno.ofneutronsfound}{Totalno.offissionevents}$

This is an experimental work and the number comes to be almost 2.4.
Remember these neutrons trigger the next fission reaction and we get a "Self - Sustaining Chain Reaction".