Question

Determine the unknown term in the following decay reactions and calculate the total energy emitted. What is the meaning of this energy?

a) 238U → ? + 4He

b) 137Cs → ? + (_-1^0)e +v ̅

c) 3H → ? + (_-1^0)e+v ̅

Answer 1

a)

Here, alpha emission occurs. So. Mass number and an atomic number both will change.

compare mass number:

238= X+4*4

X=238-16=222

222 is the mass number of Rn.

Energy Emission=

=

Energy Emission =

=

The reaction is an exothermal reaction.

b)

Here, beta emission takes place.so only considerable change occurs in an atomic number.

Cs atomic number is 55.

56 is the atomic number of Ba.

Energy Emission=

=

The reaction is an exothermal reaction.

c)

Beta emission results in the increase by one unit in the atomic number of an atom.

Energy emission=

​

Energy emission=

The value of energy emission is negative. the negative sign indicates reaction is endothermal.so, we need to add energy to the reaction complete.