Identify the missing species and the radioactive decay process?

a) 23994Pu+10nAZ+9436Kr+210n

b) 23392+10n13351Sb+AZ?+310n

c) 12856Ba+01eAZ?+γ

d) AZ?+01e8135Br+γ

1 Answer
Jan 7, 2017

For convenience, the original questions are copied down below.

a) 23994Pu+10nAZ+9436Kr+210n

When you set up the system of equations to solve this by asserting conservation of mass, just look across the top and across the bottom to get:

239+1=A+94+2(1)
94+0=Z+36+2(0)

Solving each one gives:

A=239+1942=144
Z=94+0362(0)=58

So, your isotope has an atomic number of 58 and a mass number of 144, meaning that it is cerium-144, 14458Ce.

Nuclear fission is by definition absorbing a neutron and then splitting into two atoms and releasing a couple of neutrons.

b) 23392+10n13351Sb+AZ?+310n

Set up the system of equations:

233+1=133+A+3(1)
92+0=51+Z+3(0)

Solving these gives:

A=233+11333=98
Z=92+0513(0)=41

Atomic number 41 is niobium, so we have 9841Nb. This is also nuclear fission for the same reason as in a.

c) 12856Ba+01eAZ?+γ

The missing product is 12855Cs.

Since the isotope absorbs an electron to combine with a proton and form a neutron, A stays the same but Z decreases by 1, so I'd call this electron capture.

d) AZ?+01e8135Br+γ

This is just a variation on l. So, it's electron capture, and the missing reactant is 8136Kr.