Radiochemistry and Radioactivity
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Questions and Answers

What is an isotope with a balanced number of neutrons and protons called?

  • Ion
  • Radioisotope
  • Molecule
  • Stable isotope (correct)

    • What happens to the activity of a radioactive source over time?

  • It increases
  • It becomes zero immediately
  • It remains constant
  • It decreases (correct)

    • What is a radioisotope?

  • An inert gas
  • An isotope that is unstable and emits radiation (correct)
  • A stable isotope with no radiation
  • A form of an atom with more electrons

    • What is the half-life of a radioactive source?

    <p>The time taken for the activity to fall to half its original value</p> Signup and view all the answers

    What occurs during the decay process of a radioisotope?

    <p>The radioisotope becomes less radioactive over time</p> Signup and view all the answers

    Which statement best explains why a radioisotope becomes weaker over time?

    <p>It becomes stable</p> Signup and view all the answers

    What did early investigations by Becquerel, the Curies, Rutherford, and Soddy show?

    <p>The activity of a radioactive source reduces over time</p> Signup and view all the answers

    How does the activity of a radioactive source fall over time?

    <p>At an exponentially decreasing rate</p> Signup and view all the answers

    What is the charge of a gamma ray?

    <p>0</p> Signup and view all the answers

    Which type of decay involves the emission of a helium nucleus?

    <p>Alpha decay</p> Signup and view all the answers

    What is the general equation for beta decay?

    <p>$ ^{A}<em>{Z}X ightarrow ^{A-1}</em>{Z+1}Y + ^0_-1e $</p> Signup and view all the answers

    What occurs during ionization?

    <p>An electron gains enough energy to break away from an atom.</p> Signup and view all the answers

    Which particle has a charge of 1+?

    <p>Positron</p> Signup and view all the answers

    What is the result of the beta decay of carbon-14?

    <p>Nitrogen-14</p> Signup and view all the answers

    What type of radiation is emitted when an excited nucleus returns to its ground state?

    <p>Gamma ray</p> Signup and view all the answers

    Which nuclear reaction correctly represents the alpha decay of radium-226?

    <p>$ ^{226}<em>{88}Ra \rightarrow ^{222}</em>{86}Rn + ^4_2\alpha $</p> Signup and view all the answers

    Which of the following types of radiation is known to cause 10 times more biological damage than beta radiation of the same energy?

    <p>Alpha radiation</p> Signup and view all the answers

    Which process is dominant for high radiation levels?

    <p>Direct action</p> Signup and view all the answers

    Approximately how much of x-ray damage is due to indirect action?

    <p>2/3</p> Signup and view all the answers

    Which of the following is NOT a common method of detecting ionizing radiation?

    <p>Thermoluminescent dosimeter</p> Signup and view all the answers

    What is the medium used in gas-filled detectors for detecting ionizing radiation?

    <p>Gas</p> Signup and view all the answers

    What type of radiation do gas-filled detectors primarily measure?

    <p>Gamma-rays and beta-particles</p> Signup and view all the answers

    Which isotope has a half-life of 8 days?

    <p>I-131</p> Signup and view all the answers

    Which isotope is used in the treatment of leukemia?

    <p>P-32</p> Signup and view all the answers

    Which isotope has a half-life of 15 hours?

    <p>Na-24</p> Signup and view all the answers

    For which type of cancer is Co-60 primarily used?

    <p>Different types of cancer</p> Signup and view all the answers

    Which isotope has the longest half-life among the ones listed?

    <p>Fe-59</p> Signup and view all the answers

    What does the mass number (A) represent in the nuclide $^{127}I_{53}$?

    <p>The total number of nucleons</p> Signup and view all the answers

    What is the charge of an alpha particle?

    <p>+2</p> Signup and view all the answers

    Which type of radiation is a stream of electrons?

    <p>Beta radiation</p> Signup and view all the answers

    Which type of radiation is a form of high-energy electromagnetic wave?

    <p>Gamma radiation</p> Signup and view all the answers

    How many protons does the nuclide $^{127}I_{53}$ have?

    <p>53</p> Signup and view all the answers

    What kind of radiation causes skin burns?

    <p>Beta radiation</p> Signup and view all the answers

    What does radioactivity involve?

    <p>Spontaneous emission of energetic radiations</p> Signup and view all the answers

    Which of the following isotopes is naturally present in our bodies?

    <p>Potassium-40</p> Signup and view all the answers

    What are the protons and neutrons in the nucleus collectively called?

    <p>Nucleons</p> Signup and view all the answers

    What is the SI unit for measuring radioactivity?

    <p>Becquerel</p> Signup and view all the answers

    How many disintegrations per second are equivalent to one curie?

    <p>3.7 x 10^10</p> Signup and view all the answers

    What is the atomic number of an atom symbolized by?

    <p>Z</p> Signup and view all the answers

    What is the charge of a neutron?

    <p>0 unit</p> Signup and view all the answers

    Which isotope of hydrogen contains two neutrons?

    <p>Tritium</p> Signup and view all the answers

    Which uranium isotope has 92 protons and 146 neutrons?

    <p>Uranium-238</p> Signup and view all the answers

    What is the overall charge on an atom in its normal state?

    <p>Zero</p> Signup and view all the answers

    Which of the following isotopes is specifically produced for medical use?

    <p>Iodine-131</p> Signup and view all the answers

    Approximately how much heavier is a nucleon compared to an electron?

    <p>2000 times</p> Signup and view all the answers

    What holds the electrons in orbit around the nucleus?

    <p>Electrostatic attraction</p> Signup and view all the answers

    What distinguishes isotopes of the same element from each other?

    <p>Number of neutrons</p> Signup and view all the answers

    How is the mass number, A, of an atom calculated?

    <p>A = Z + N</p> Signup and view all the answers

    What term describes a particular nuclear species with a given combination of A and Z?

    <p>Nuclide</p> Signup and view all the answers

    What type of energy does ionizing radiation possess compared to non-ionizing radiation?

    <p>More energy</p> Signup and view all the answers

    Which type of radiation is at the upper end of the electromagnetic spectrum?

    <p>X-ray and gamma ray radiation</p> Signup and view all the answers

    What happens to an atom when exposed to very high-energy ionizing radiation?

    <p>The atom loses electrons or the nucleus breaks up</p> Signup and view all the answers

    Which tissue type is particularly sensitive to radiation damage?

    <p>Bone marrow</p> Signup and view all the answers

    Which particles are around twenty times as effective at killing cells compared to beta particles, gamma rays or X-rays?

    <p>Alpha particles</p> Signup and view all the answers

    What is the unit for absorbed dose of radiation?

    <p>RAD</p> Signup and view all the answers

    What does REM stand for in the context of radiation dose measurements?

    <p>Relative Biological Equivalence</p> Signup and view all the answers

    How much energy is equal to one rad?

    <p>$2.4 \times 10^{-3}$ cal</p> Signup and view all the answers

    Study Notes

    Radiochemistry

    • Radioactivity is a natural phenomenon that occurs in certain substances, where atoms emit invisible and energetic radiations that can penetrate materials opaque to visible light.
    • These radiations can be harmful to live cells, but they have beneficial applications in medicine when used correctly.

    Units of Radioactivity

    • The amount of radioactivity is measured by the rate of radioactive disintegration per second.
    • The Curie (Ci) is a unit of radioactivity, equivalent to 3.7 x 10^10 disintegrations per second.
    • 1 Curie is equal to 3.7 x 10^10 Becquerel.

    Isotopes

    • An isotope is a variant of a chemical element, with the same number of protons (atomic number) but a different number of neutrons.
    • Isotopes can be stable or radioactive, and radioisotopes undergo spontaneous decay and emit radiation.
    • The stability of an isotope depends on the balance of neutrons and protons.

    Radioisotopes

    • Radioisotopes are isotopes that undergo spontaneous decay and emit radiation.
    • They become less radioactive over time, eventually becoming stable.
    • The half-life of a radioisotope is the time it takes for the activity to fall to half of its original value.

    Half-Life

    • The half-life of a radioactive source is the time it takes for the activity to fall to half of its original value.
    • The activity of a radioisotope decreases exponentially with time, halving every half-life.
    • The half-life of a radioisotope is different for each substance.

    The Atom

    • An atom is the smallest unit of matter, consisting of a nucleus and orbiting electrons.
    • The nucleus is composed of protons and neutrons, and the number of protons determines the atomic number (Z).
    • The atomic number and mass number (A) determine the identity of an element.

    Structure of the Atom

    • The nucleus is composed of protons and neutrons.
    • The atomic number (Z) is the number of protons in the nucleus.
    • The mass number (A) is the sum of protons and neutrons in the nucleus.

    Types of Radiation

    • Alpha radiation is a stream of particles with two protons and two neutrons, having a charge of +2.
    • Beta radiation is a stream of electrons, resulting from the transformation of a neutron into a proton and electron.
    • Gamma radiation is a form of energy, similar to light waves or X-rays, with high energy and penetration.
    • Electron Capture or Ionization radiation is a process where an electron is given enough energy to break away from an atom.

    Nuclear Reaction

    • Nuclear reactions involve the collision of atomic nuclei or a nucleus and a subatomic particle.
    • The resulting nuclides are different from the parent nuclei.

    Forms and Properties of Nuclear Radiation

    • Alpha radiation has a charge of +2 and a symbol of α or 4He.
    • Beta radiation has a charge of -1 and a symbol of β or -10e.
    • Gamma radiation has a charge of 0 and a symbol of γ.
    • Positron radiation has a charge of +1 and a symbol of +10e.
    • Neutron radiation has a charge of 0 and a symbol of n.

    Ionization Radiation

    • Ionization radiation is the process where an electron is given enough energy to break away from an atom.
    • This results in the formation of two charged particles or ions: a positively charged molecule and a negatively charged electron.

    Alpha Decay

    • Alpha decay occurs when a nucleus with a mass number greater than 200 liberates a helium nucleus (alpha particle).
    • The general equation for alpha decay is: A-ZX → A-4Z-2X + α.

    Beta Decay

    • Beta decay occurs when a neutron is converted into a proton, accompanied by the emission of a beta particle (high-energy electron).
    • The equation for beta decay is: A-ZX → A-Z+1X + -10e.

    Gamma Emission

    • Gamma emission occurs when an excited nucleus returns to its ground state, accompanied by the emission of a high-energy photon.
    • The equation for gamma emission is: A-ZX → A-ZX + γ.

    Ionizing Radiation

    • Ionizing radiation is energy produced from natural or artificial sources, with enough energy to cause chemical changes in living tissue.
    • X-ray and gamma ray radiation are at the upper end of the electromagnetic spectrum, with high frequencies and short wavelengths.
    • Ionizing radiation deposits a large amount of energy into a small area, disrupting chemical bonds and causing damage.

    Radiation Dose

    • Radiation dose measures the energy deposited by ionizing radiation in a material.
    • The concept of absorbed dose applies to all types of material, but when assessing biological effects, the equivalent dose is used, which takes into account the radiation weighting factor.
    • The equivalent dose is measured in units of Rem, which is 1 rad multiplied by the relative biological equivalence (RBE).

    Units of Radiation Dose

    • Rad is a unit of radiation dose, equivalent to 2.4 x 10^-3 cal of energy absorbed by 1 kg of tissue.
    • Rem is a unit of radiation dose, equivalent to 1 rad multiplied by the RBE.

    Direct and Indirect Action

    • Direct action occurs when the atoms of the target are ionized by the radiation.
    • Indirect action occurs when the radiation interacts with other cellular molecules, producing free radicals that damage the target.

    Radiation Detectors

    • The three methods of detecting ionizing radiation are the photographic method, scintillation counter, and Geiger counter.
    • Geiger counters are gas-filled detectors that use an electric potential to collect electrons released by ionizing radiation.

    Medical Applications of Isotopes

    • The half-life of an isotope must be long enough for it to do its job and short enough to eliminate it from the body.
    • In medical applications, no alpha radiation is used due to its damaging effects on tissues.
    • The main mechanism for isotopes application is either externally (such as Co-60) or internally (such as I-131).
    • The table below shows the main isotopes used in medical applications:
    Isotopes Half-life Application
    I-131 8 days Thyroid cancer
    Co-60 5.3 years Different types of cancer
    P-32 143 days Leukemia
    Na-24 15 hrs Circulation system
    Fe-59 456 days Red blood cells

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    Learn about the natural phenomenon of radioactivity, its effects on living cells, and its beneficial applications in medicine.

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