Isotopes

Key Notes:

Definition of Isotopes:

  • Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons.
  • This means isotopes have the same atomic number but different mass numbers.

Example of Isotopes:

  • The most common example is Carbon:
    • Carbon-12 has 6 protons and 6 neutrons.
    • Carbon-13 has 6 protons and 7 neutrons.
    • Carbon-14 has 6 protons and 8 neutrons.
  • Despite having different mass numbers, all three isotopes of carbon behave chemically the same.

Atomic Number and Mass Number:

  • Atomic number (Z) represents the number of protons in the nucleus and remains the same for isotopes of an element.
  • Mass number (A) is the sum of protons and neutrons in the nucleus and varies among isotopes.

Representation of Isotopes:

  • Isotopes are denoted using the element symbol followed by the mass number. For example, Carbon-12 (12C)

Physical vs. Chemical Properties:

  • Isotopes of an element have identical chemical properties because they have the same electron configuration.
  • They may have different physical properties like density, melting point, and stability due to differences in mass.

Radioactive Isotopes:

  • Some isotopes are radioactive, meaning they decay over time and emit radiation. These are called radioisotopes.
  • Example: Uranium-238 is a radioactive isotope used in nuclear reactors, while Carbon-14 is used in carbon dating to determine the age of fossils.

Applications of Isotopes:

  • Medical: Radioisotopes like Cobalt-60 are used in cancer treatment and diagnostic imaging.
  • Agriculture: Isotopes are used in tracing nutrient uptake in plants.
  • Archaeology: Carbon-14 dating helps determine the age of ancient artifacts.

Stable vs. Unstable Isotopes:

  • Stable isotopes do not change over time and do not emit radiation.
  • Unstable isotopes (radioisotopes) undergo radioactive decay and can transform into other elements.

Isotopes in Nature:

  • Elements in nature often exist as mixtures of their isotopes. For example, chlorine is a mix of Chlorine-35 and Chlorine-37.
  • The average atomic mass of an element on the periodic table is a weighted average of its naturally occurring isotopes.

Importance of Isotopes:

  • Isotopes play a crucial role in scientific research, medicine, environmental studies, and understanding the history of Earth and space.

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