Nitrogen is the N and that is what is the element is the reactant in excess.
The decay mode of cesium-137 is beta decay. This means that the cesium-137 decays into a beta particle and a nuclide with the same mass number, but with a charge number that is 1 more than that of cesium.
Therefore, this means Cs-137 decays into an electron and Barium-137, meaning the answer is choice 1.
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Your answers would 35/3, 11 2/3, and 11.6 !! :D