Assignment:
Question 1. The naturally occurring isotopes of potassium are:
39 K (abundance 93.10%)
40 k (abundance 0.0118%)
41 k (abundance 6.88%)
40K is radioactive and decays by Beta- decay with a half-life of 1.29 multiplied by 10`9 years.
a) How many protons and neutrons does each of the three isotopes of potassium have?
b) Calculate the atomic weight of naturally occurring potassium.
c) What is the daughter nucleus of 40K? Explain why.
d) What percentage of 40K nuclei will decay in the next 10 000 years?
e) What is the value in second-1 of the decay constant (y - this should be an upside down y) for 40k?
f) Using the definitions for the decay constant and for the becquerel, calculate the activity of 1 gram of naturally occurring potassium.
(Note: 6.02 multiplied by 10`23 (i.e. 1 mole) atoms of any element will have a mass in grams equal to its atomic weight, for example, 6.02 multiplied by 10`23 atoms of calcium will weigh 40.08 grams.)