5.2.3. Radioactive decay
A subsection of Physics, 5054, through 5. Nuclear physics
Listing 10 of 23 questions
Some atoms that undergo radioactive decay have a half-life of 6 hours. The count rate near a sample of these atoms is initially 838 counts/minute. Background radiation near the sample is 18 counts/minute. Describe the structure of an atom. It may help to draw a diagram. Explain what is meant by radioactive decay. State clearly which part of the atom decays. State what is meant by background radiation. The equipment is left undisturbed for 12 hours. Calculate the count rate due to the sample of atoms alone after this time. The table shows a radioactive series. Atom A emits a beta-particle and becomes atom B. Atom B then emits a particle to become atom C. Calculate the proton number X of atom B and explain how you calculated it. State the name of radiation Y and describe the changes that occur in the atom when this radiation is emitted. Using information from the table, explain why atoms A and C are not isotopes of the same element. atom A B C proton number (atomic number) nucleon number (mass number) radiation emitted beta-particle X Y none
5054_s05_qp_2
THEORY
2005
Paper 2, Variant 0
View
A hospital laboratory uses a small sample of a radioactive isotope of iodine, 13 3I. Describe the structure of the nucleus of an atom of this isotope. The sample is radioactive. Describe what happens in radioactive decay. The count in one minute from the source is measured several times. shows the readings obtained. Suggest why the readings are different. The half-life of 131 53I is 8.0 days. Estimate the count in one minute obtained from the sample after 24 days. count =
5054_s14_qp_21
THEORY
2014
Paper 2, Variant 1
View
A doctor has the choice of two isotopes, 131 53I and 125 53I, to inject into a patient. These isotopes emit radiation from deep inside the body. The radiation is detected outside the body and provides information to help the doctor find out what is wrong with the patient. The isotope 131 53I decays into a stable isotope of xenon by emitting a beta-particle (β) and a gamma ray (γ). State what is meant by a gamma ray. Complete the equation to show the radioactive decay of 131 53I. 53I Xe + −1β + γ When a nucleus of 125 53I decays, only a gamma ray is emitted. Suggest why it is better for the doctor to inject the isotope 125 53I into the patient.
5054_s17_qp_21
THEORY
2017
Paper 2, Variant 1
View
Radon-222 is an isotope of radon which undergoes a series of radioactive decays. is a diagram showing the proton number (atomic number) and nucleon number (mass number) of nuclei involved in the series of decays. The point P represents a nucleus of radon-222. Starting at P, a nucleus of radon-222 decays to Q; then from Q to R; then from R to S; then from S to T; and finally from T to U. proton number nucleon number P Q R T U S State two points on which represent isotopes of the same element. Different isotopes of the same element have different atomic compositions. State how the composition of their atoms is different. A nucleus of radon-222 emits an alpha-particle as it decays. The radioactive decay of a single nucleus is random. Explain what is meant by the random radioactive decay of a nucleus. In nuclide notation, radon-222 is written as 222 86Rn. When a nucleus of radon-222 emits an alpha-particle (α), it decays to an isotope of polonium (Po). Complete the decay equation below for this decay. 86Rn → Po + α State the name of the particle emitted as a nucleus of R decays to a nucleus of S. Describe the change in the composition of a nucleus of R as it decays to a nucleus of S.
5054_s20_qp_22
THEORY
2020
Paper 2, Variant 2
View
Alpha particles are sometimes emitted from the nuclei of radioactive elements. This emission is both random and spontaneous. Describe what is meant by ‘spontaneous’ emission. Describe the composition of an alpha particle. Alpha particles are detected using the tracks shown in a cloud chamber or by the sparks produced in a spark counter. Describe the structure of either a cloud chamber or a spark counter. Include a labelled drawing of the apparatus. Describe how the emission of alpha particles is shown as random in the apparatus you described in . A radioactive source produces 120 tracks in one minute in a cloud chamber. 6.0 hours later, the same source produces 15 tracks in one minute. Without the source present, no tracks are produced. Calculate the half-life of the radioactive isotope in the source. half-life = hours
5054_s24_qp_22
THEORY
2024
Paper 2, Variant 2
View
Questions Discovered
23