Why Is Krypton the Product in This Nuclear Reaction?

[Hooly]

Can someone please explain to me why the answer to the following question is Krypton? A step by step solution would be ideal please!

(b)The following reaction occurs in a nuclear reactor:

235U+01n →141Ba+X+301n+202.5MeV
(i) Identify the element X.

Many thanks!
(Question is Q12 b part i from the 2010 Irish state physics exam http://examinations.ie/archive/exampapers/2010/LC021ALP000EV.pdf )

 

[Greg Bernhardt]

What do you know about the problem? What have you tried?

 

[Hooly]

I initially took this approach;
235 + 1 -141 -3(1) which is equal to 92. When I checked the answer this was incorrect. Then went down the route of converting the MeV to joules and subbing that value into the mass- energy equivalence formula in order to find the mass, and then using the unified atomic mass unit value (1.6605402x10^-27 kg) to try to find the element represented by the energy, at which point I got lost and have been unable to proceed further. Bear in mind I am 18 and studying for my Leaving Cert in Ireland (equivalent of SATs in US I think) so I am not at an advanced level

 

[mfb]

Which number determines the chemical element?

 

[Hooly]

Do you guys just reply with questions? :P But yes I realized earlier that atomic number was the way to go, wasn't thinking straight, over complicated it. Many thanks

 

[mfb]

Do you guys just reply with questions? :P

The idea is to help you to find the answer, and questions often work best.