Stable and unstable isotopes are important ideas in understanding atomic structure and isotopes, especially in Year 11 Physics. Knowing how they differ is key to learning about nuclear chemistry and radioactivity.

What Are Isotopes?

• Isotopes: These are different forms of a chemical element. They have the same number of protons but different numbers of neutrons in their atomic nuclei. This makes their atomic masses different.
  • For example, Carbon-12 ($^{12}\text{C}$) has 6 protons and 6 neutrons. On the other hand, Carbon-14 ($^{14}\text{C}$) has 6 protons and 8 neutrons.

Stable Isotopes

• What They Are:
  • A stable isotope does not change over time and does not undergo radioactive decay.
• Examples: Here are some common stable isotopes:
  • Hydrogen-1 ($^{1}\text{H}$): 1 proton, 0 neutrons
  • Carbon-12 ($^{12}\text{C}$): 6 protons, 6 neutrons
  • Oxygen-16 ($^{16}\text{O}$): 8 protons, 8 neutrons
• How Common Are They?: Stable isotopes make up most of the isotopes for each element. For example, about 98.89% of carbon found in nature is Carbon-12 ($^{12}\text{C}$).

Unstable Isotopes

• What They Are:
  • Unstable isotopes, also called radioactive isotopes, change over time. They transform into different elements and release radiation during this change.
• Decay Rates: Each unstable isotope changes at its own rate, which is measured in half-lives. A half-life is the time it takes for half of a sample of the isotope to change.
  • For example, Carbon-14 ($^{14}\text{C}$) has a half-life of about 5,730 years. After this time, half of a sample of Carbon-14 will have turned into Nitrogen-14 ($^{14}\text{N}$).
• Examples: Some common unstable isotopes are:
  • Uranium-238 ($^{238}\text{U}$): Half-life of about 4.5 billion years
  • Plutonium-239 ($^{239}\text{Pu}$): Half-life of around 24,100 years
  • Radon-222 ($^{222}\text{Rn}$): Half-life of about 3.8 days

Uses of Isotopes

1. Stable Isotopes:
   • They are used a lot in medicine and science. For example, Deuterium ($^{2}\text{H}$) is used in a technique called NMR spectroscopy.
   • They are also important for carbon dating. This process uses stable isotopes to find out the age of things.
2. Unstable Isotopes:
   • These isotopes are crucial in nuclear energy and weapons. The energy released when they decay, like with Uranium-235 ($^{235}\text{U}$), can be used to make electricity.
   • They are also used in medical treatments, like radiation therapy for cancer. Isotopes like Iodine-131 ($^{131}\text{I}$) are used in this type of treatment.

Summary

To wrap it up, the main difference between stable and unstable isotopes is their stability. Stable isotopes do not change and stay the same, while unstable isotopes change over time, turning into different elements and releasing radiation. This understanding is important in learning about atomic structure and isotopes in Year 11 Physics.