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    Chemistry worksheet
    Topic: Mode And Rate Of Decay

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    Mode And Rate Of Decay
    1

    Which particle has the least mass?

    (1) alpha particle

    (2) beta particle

    (3) neutron

    (4) proton

    2

    Which nuclear emission has the greatest penetrating power?

    (1) proton

    (2) beta particle

    (3) gamma radiation

    (4) positron

    3

    Which statement describes the relative masses of two different particles?

    (1) A neutron has less mass than a positron.

    (2) A beta particle has less mass than a neutron.

    (3) An alpha particle has less mass than a positron.

    (4) An alpha particle has less mass than a beta particle.

    4

    When an atom of the unstable isotope Na-24 decays, it becomes an atom of Mg-24 because the Na-24 atom spontaneously releases

    (1) an alpha particle

    (2) a beta particle

    (3) a neutron

    (4) a positron

    5

    Positrons and beta particles have

    (1) the same charge and the same mass

    (2) the same charge and different masses

    (3) different charges and the same mass

    (4) different charges and different masses

    6

    Which balanced equation represents a spontaneous radioactive decay?

    (1) 14C + Ca3(PO4)2 → 3CaC2 + 2P + 8CO

    (2) 147N + 10n → 1466C + 11p

    (3) H2CO3 → H2O + CO2

    (4) 146C → 147N +0-1e

    7

    Which nuclear emission is negatively charged?

    (1) an alpha particle

    (2) a beta particle

    (3) a neutron

    (4) a positron

    8

    A sample of which radioisotope emits particles having the greatest mass?

    (1) 137Cs

    (2) 53Fe

    (3) 220Fr

    (4) 3H

    9

    An unstable nucleus spontaneously releases a positron. This is an example of

    (1) radioactive decay

    (2) nuclear fusion

    (3) chemical decomposition

    (4) thermal conductivity

    Base your answers to questions 10 on the information below.

    Nuclear radiation is harmful to living cells, particularly to fast-growing cells, such as cancer cells and blood cells. An external beam of the radiation emitted from a radioisotope can be directed on a small area of a person to destroy cancer cells within the body.

    Cobalt-60 is an artificially produced radioisotope that emits gamma rays and beta particles. One hospital keeps a 100.0-gram sample of cobalt-60 in an appropriate, secure storage container for future cancer treatment.

    10

    Compare the penetrating power of the two emissions from the Co-60.

    Allow 1 credit. Acceptable responses include, but are not limited to:

    • Gamma radiation has greater penetrating power.

    • Beta particles have weaker penetrating power.

    Base your answers to questions 11 on the information below and on your knowledge of chemistry.

    In 1896, Antoine H. Becquerel discovered that a uranium compound could expose a photographic plate wrapped in heavy paper in the absence of light. It was shown that the uranium compound was spontaneously releasing particles and high-energy radiation. Further tests showed the emissions from the uranium that exposed the photographic plate were not deflected by charged plates.

    11

    Identify the highly penetrating radioactive emission that exposed the photographic plates.

    Allow 1 credit. Acceptable responses include, but are not limited to:

    • gamma radiation

    • gamma

    • γ

    • X-ray radiation

    Base your answers to questions 12 on the information below and on your knowledge of chemistry.

    Cobalt-60 is an artificial isotope of Co-59. The incomplete equation for the decay of cobalt-60, including beta and gamma emissions, is shown below.

    atomic-concepts, isotopes-atomic-mass, periodic-table, identification-of-element fig: chem62019-exam_g13.png

    12

    Compare the penetrating power of the beta and gamma emissions.

    Allow 1 credit. Acceptable responses include, but are not limited to:

    • The gamma radiation has more penetrating power than the beta emission.

    • The β− is less penetrating than γ.

    • Gamma emissions have greater penetrating power.

    Base your answers to questions 13 on the information below and on your knowledge of chemistry.

    One fission reaction for U-235 is represented by the balanced nuclear equation below.

    nuclear-chemistry, nuclear-reactions fig: chem82015-exam_g9.png

    Both radioisotopes produced by this fission reaction undergo beta decay. The half-life of Xe-140 is 13.6 seconds and the half-life of Sr-94 is 1.25 minutes.

    13

    On the diagram below, draw an arrow to represent the path of an emitted beta particle in the electric field between two oppositely charged metal plates.

    nuclear-chemistry, mode-and-rate-of-decay fig: chem82015-abkq65.png

    Allow 1 credit.

    • Examples of 1-credit responses:

    • chem82015-rg_g1.png

    Base your answers to questions 14 on the information below and on your knowledge of chemistry.

    Radioactive emissions can be detected by a Geiger counter. When radioactive emissions enter the Geiger counter probe, which contains a noble gas such as argon or helium, some of the atoms are ionized. The ionized gas allows for a brief electric current. The current causes the speaker to make a clicking sound. To make sure that the Geiger counter is measuring radiation properly, the device is tested using the radioisotope Cs-137.

    To detect gamma radiation, an aluminum shield can be placed over the probe window, to keep alpha and beta radiation from entering the probe. A diagram that represents the Geiger counter is shown below.

    periodic-table, characteristic-trends fig: chem82019-exam_g13.png

    14

    State evidence from the passage that gamma radiation has greater penetrating power than alpha or beta radiation.

    Allow 1 credit. Acceptable responses include, but are not limited to:

    • The gamma radiation has much greater penetrating power because it can pass through the aluminum shield.

    • The alpha and beta particles cannot penetrate the aluminum shield.

    • The aluminum shield does not stop gamma radiation.

    Base your answers to questions 15 on the information below and on your knowledge of chemistry.

    The diagram below shows the first three steps in the uranium-238 radioactive decay series.

    atomic-concepts, isotopes-atomic-mass, periodic-table, identification-of-element fig: chem12018-exam_g15.png

    The decay mode for the first and third steps is shown above the arrows. The decay mode for the second step is not shown in the diagram. Thorium-234 has a half-life of 24.10 days.

    15

    Identify the decay mode particle emitted from the Th-234.

    Allow 1 credit. Acceptable responses include, but are not limited to:

    • beta particle

    • beta

    • β−

    • 0−1 β

    • 0−1e

    • electron