Elements

• Definition of an Element

  • An element is defined as a substance that contains only one type of atom.

• Current Number of Elements

  • There are currently 117 elements known to exist.

  • Naturally Occurring Elements: 91 elements are naturally occurring.

  • Officially Named Elements: 114 elements have official names.

• Atomic Symbols

  • Each element has a unique atomic symbol, represented by one or two letter abbreviations.

  • Examples of Atomic Symbols:

    • Hydrogen = H

    • Lead = Pb

    • Calcium = Ca

Trace Elements

• Definition and Importance of Trace Elements

  • Trace elements are defined as the elements that the body needs in small amounts to function properly.

  • They are essential for biological compounds, including carbohydrates and proteins.

• Proportion in Body Weight

  • Trace elements make up less than 0.1% of total body weight.

  • The adult daily requirement for these elements is less than 100 mg.

• Nutritional Labels

  • Nutrition Facts Labels are utilized to help consumers understand the nutritional content of food products.

Radioactive Isotopes

• Definition of Nuclear Change

  • Nuclear change involves changes to atomic nuclei, resulting in something new being created, which alters the identity of the atom.

  • More than 300 naturally occurring isotopes have been identified.

• Nuclear Radiation

  • Nuclear radiation consists of the particles and energy released during a nuclear change.

  • Atoms that emit nuclear radiation are referred to as radioactive isotopes or radioisotopes.

• Common Forms of Radiation

  • Alpha Particle (α)

  • Identical to the nucleus of a helium-4 atom, consisting of two protons and two neutrons, with a 2+ charge.

  • Has higher energy due to its velocity.

  • Beta Particle (β)

  • An electron that is ejected from the nucleus of a radioisotope, traveling at approximately 90% of the speed of light.

  • Has identical charge and mass as an electron.

  • Positron (β+)

  • Same mass as a beta particle but carries a 1+ charge.

  • Ejected at 90% of the speed of light and used in medical procedures, specifically positron emission tomography.

  • Gamma Particle (γ)

  • A high-energy form of electromagnetic radiation.

  • Often occurs in conjunction with the release of alpha, beta, or positron radiation.

• Alpha Particle Emission Example

  • When a radioactive isotope emits an alpha particle:

  • The product has two fewer protons and neutrons.

  • Reaction Example:

    • $^{230}<em>{90}Th ightarrow ^{226}</em>{88}Ra + ^{4}_{2}α$.

• Beta Particle Emission Example

  • When a radioactive isotope emits a beta particle:

  • The product has one more proton and one less neutron.

  • Reaction Example:

    • $^{12}<em>{5}B ightarrow ^{12}</em>{6}C + ^{0}_{-1}β$.

• Positron Emission Example

  • When a radioactive isotope emits a positron:

  • The product has one less proton and one more neutron.

  • Reaction Example:

    • $^{18}<em>{9}F ightarrow ^{18}</em>{8}O + ^{0}_{1}β^+$.

• Gamma Ray Emission Example

  • During gamma emissions, energy is given off as the nucleus rearranges to a more stable form.

  • Reaction Example:

  • $^{131}<em>{53}I ightarrow ^{131}</em>{54}Xe + ^{0}<em>{-1}β + ^{0}</em>{0}γ$.

• Nuclear Equation Balancing Example

  • Fill in the missing items from the following nuclear equation:

  • $^{81}<em>{37}Rb + ^{0}</em>{-1}β <br>ightarrow ?$.

• Penetrating Power of Radiation

  • Question: Which radioactive particle has the lowest penetrating power?

  • Choices: a. alpha b. beta c. positron d. gamma

Radioisotopes in Medicine

• Effects of Nuclear Radiation

  • Nuclear radiation can transfer kinetic energy to surrounding atoms when coming into contact with matter, leading to changes in water and disruption of biochemical processes.

• Half-life of a Radioisotope

  • The half-life of a radioisotope is defined as the time required for one-half of the atoms in a sample to decay.

  • Understanding the half-life is important in medical applications:

  • Medical professionals aim for minimal exposure to radiation, so shorter half-lives are preferred.

• Medical Applications of Radioisotopes

  • Radioisotopes in Diagnosis and Therapy:

  • Radiation therapy often employs gamma rays, specifically from cobalt-60, targeted towards tumor sites, but can cause radiation sickness due to effects on healthy tissue.

  • Internal Therapy:

    • Example: Treatment of thyroid conditions with iodine-131.

    • Involves larger doses than diagnostic uses, as iodine is incorporated into hormones that concentrate in the thyroid gland, with beta rays not penetrating more than several millimeters.

• Question on Nuclear Radiation

  • Which form of nuclear radiation is comprised of electromagnetic radiation?

  • Choices: a. alpha b. beta c. positron d. gamma