Radon gas , 222 86 Rn, is formed by alpha decay. a. Write down the reaction for
ID: 1468767 • Letter: R
Question
Radon gas , 222 86 Rn, is formed by alpha decay. a. Write down the reaction for this reaction. What is the parent nucleus for this reaction? b. Using the data in Appendix C of the book, calculate the Q-value for this reaction. c. Ignoring the KE of the daughter nucleus (because it is so massive), what is the kinetic energy of the alpha particle? d. Estimate the magnitude of the momentum of the daughter nucleus and of the alpha particle. e. Estimate the KE of the daughter nucleus from its momentum, and argue that your assumption in part (c) was valid.
Explanation / Answer
An Alpha decay is when an element's ATOMIC NUMBER decreases by TWO, the number of NEUTRONS decreases by TWO, the number of PROTONS decreases by TWO, and the MASS number decreases by FOUR.
Radon-222 has the Atomic Number of 86 in the Periodic table.
The Atomic number decreases by two and the Atomic mass decreases by 4. 86 turns to 84, 222 turns to 218.
It would look like this
Radon-222 -----> 4He + 218 Polonium
..........86...........2............ 84
4He is known as an Alpha Decay.
The element produced would be Polonium-218
Radon = 222 amu
Polonium = 209 amu
Helium = 4.002602 amu
:- 222 = 4 × 4.002602 + 209
222 - 16.010408 - 209 = - 3.010408 amu
Mass is decrease means energy is release.
Q- value = 3.010408 amu × 931.5 MeV/amu
= 2804.1950 MeV.
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