Question

2)Each of the nuclides listed below decays either by beta emission or by positron emission. Predict which type of decay each will undergo and select the nuclides that decay by beta emission. This list contains three beta emitters and three positron emitters.

¹¹⁷₄₇Ag

²⁰⁶₈₀Hg

²⁴₁₃Al

⁸₅B

¹⁵₆C

¹⁰₆C

Answer 1

n/p ratio is greater than 1, then nuclide emitting the beta particle. i.e. neutrons are convets to proton by the emission of Beta particle

         ₀ n¹ ----------------- ₁P¹ + _-1 e⁰  

neutron                     proton      beta particle

n/p ratio is less than 1, then nuclide emitting the positron. i,e, protons are convets to neutrons.

₁P¹   ---------------- ₀ n¹ + ₊₁ e ⁰

proton            neutron         positron

11747Ag

number of protons = 47

mass number = 117

number of neutrons = mass number - number of protons = 117 - 47 =70

So number of neutrons are more. i.e. n/p ratio is greater than 1. [ 70/47 =1.489]

Hence it is beta emitter

20680Hg

number of protons = 80

mass number = 206

number of neutrons = 206 - 80 = 126

n/p ratio is greater than 1. [ 126/80 = 1.575]

Hence it is beta emitter.

156C

number of protons = 6

mass number = 15

number of neutrons = 15-6 = 9

So, n/p ratio is greater than 1. Hence it is beta emitter.

2413Al

number of protons=13

mass number = 24

number of neutrons = 24-13 = 11

n/p ratio is less than 1. [ 11/13= 0.846]

So it is position emitter.

85B

number of protons = 5

mass number = 8

number of neutrons = 8-5=3

So. n/p ratio is less than 1 . [ 3/5 = 0.6]

Hence it is postion emitter.

106C

number of protons = 6

mass number = 10

number of neutrons = 10-6 =4

So , n/p ratio is less than 1 . [ 4/6=0.67]

Hence it is position emitter.