Question

What is a stable isotope? An unstable isotope?

Short answer

Stable isotopes do not decay, while unstable isotopes are radioactive and decay over time.

Step-by-step solution

Define an Isotope

Isotopes are variants of a particular chemical element that have the same number of protons but different numbers of neutrons. Each isotope of an element has a different atomic mass but the same chemical properties.

Identify Stable Isotopes

Stable isotopes are isotopes that are not radioactive. This means they do not decay over time and remain constant without changing into another element or isotope. They exist naturally in nature without any observable change.

Identify Unstable Isotopes

Unstable isotopes, also known as radioactive isotopes or radioisotopes, have nuclei that are prone to change. These isotopes decay over time, emitting radiation in the form of alpha, beta, or gamma rays, and transform into different elements or isotopes.

Key concepts

Stable Isotopes

Stable isotopes are unique versions of an element that do not undergo radioactive decay. This means that over time, they remain unchanged and do not transform into other isotopes or elements. These isotopes have balanced ratios of protons to neutrons, which makes their atomic nuclei particularly stable. Most elements found in nature include a mix of stable isotopes. These isotopes are important in various scientific fields:

• They are used in environmental studies to track processes like water cycling.
• They play a role in medicine when assessing metabolic processes.

Understanding stable isotopes can help us delve deeper into the history of the Earth, as well as the life processes of different organisms.

Unstable Isotopes

Unstable isotopes are also known as radioactive isotopes, or radioisotopes. Unlike stable isotopes, these have an imbalance in the ratio of neutrons to protons. This makes their nuclei unstable, leading them to undergo radioactive decay. During this process, they emit energy in the form of radiation.

• Unstable isotopes decay into new isotopes or elements over time.
• The rate of this transformation varies: some decay in fractions of a second, while others take millions of years.

These isotopes have widely varying applications, such as in cancer treatment through radiation therapy or in carbon dating which determines the age of archaeological finds.

Radioactive Decay

Radioactive decay is the process through which unstable isotopes emit particles or energy to reach a more stable state. This natural phenomenon involves three primary types of decay: alpha, beta, and gamma decay. Each type of decay involves the release of different particles or energy forms.

• Alpha decay releases two protons and two neutrons, resembling a helium nucleus.
• Beta decay involves the conversion of a neutron into a proton, with the emission of an electron and an antineutrino.
• Gamma decay is the release of excess energy by an unstable nucleus, emitted as gamma rays.

Radioactive decay is crucial in fields like geology and archaeology, where it helps in dating rocks and artifacts.

Atomic Mass

Atomic mass is a crucial property of isotopes, as it represents the total number of protons and neutrons in an atom's nucleus. It slightly differs from the atomic weight, which is an average that considers all isotopes of an element and their relative abundances. Isotopes of an element possess different atomic masses due to varying numbers of neutrons.

• For example, Carbon has isotopes with atomic masses of 12 and 14, known as Carbon-12 and Carbon-14.
• Knowing the atomic mass helps in calculations related to chemical reactions and molecular weights.

The concept of atomic mass is critical in understanding how isotopes exhibit the same chemical properties despite differences in mass.

Chemical Properties

Isotopes of an element, whether stable or unstable, share almost identical chemical properties. This is because chemical behavior is determined by electronic configuration, which remains constant in all isotopes of an element due to the same number of protons and electrons. As isotopes have different numbers of neutrons, they do not significantly affect chemical reactions at standard conditions.

• Chemical properties include reactions with other elements and compound formation.
• Common uses of isotopes in chemical studies include tracing reaction pathways and studying drug behavior in the body.

Understanding that isotopes retain the same chemical properties yet differ in stability and mass provides insight into their diverse applications in science.