Isotopes, Radioactive Decay, and Applications

Vocabulary flashcards covering isotopes, relative atomic mass calculations, modes of radioactive decay, and their practical applications in carbon dating, medicine, food storage, and sterilisation.

Isotopes

Atoms of the same element that have the same number of protons (same atomic number) but different numbers of neutrons (different mass numbers). They have identical chemical properties, but can differ in physical properties and radioactivity.

Relative Atomic Mass

The average mass of an element's sample that accounts for the different masses of its naturally occurring isotopes and their relative abundances. For chlorine ($75\%$ chlorine-35 and $25\%$ chlorine-37), it is calculated as $\frac{(75 \times 35) + (25 \times 37)}{100} = 35.5$.

Physical Properties of Isotopes

Properties that differ between isotopes of the same element due to differences in neutron count and mass. For example, chlorine-37 has a greater density than chlorine-35.

Chlorine Isotopes

The two naturally occurring isotopes of chlorine: chlorine-35 ($17$ protons, $17$ electrons, $18$ neutrons) and chlorine-37 ($17$ protons, $17$ electrons, $20$ neutrons).

Hydrogen Isotopes

The three isotopic forms of hydrogen: ${}^1_1\text{H}$ ($1$ proton, $1$ electron, $0$ neutrons), ${}^2_1\text{H}$ ($1$ proton, $1$ electron, $1$ neutron), and ${}^3_1\text{H}$ ($1$ proton, $1$ electron, $2$ neutrons).

Radioactive Decay

The process by which unstable atomic nuclei lose energy by emitting radiation in the form of alpha ($\alpha$), beta ($\beta$), or gamma ($\gamma$) rays.

Alpha Decay ($\alpha$ Decay)

A radioactive decay process where a nucleus emits an alpha particle, losing $2$ protons and $2$ neutrons. This decreases the atomic mass number by $4$ and the atomic number by $2$, forming a new element two places lower in the Periodic Table (e.g., Radon decaying into Polonium).

Beta Decay ($\beta$ Decay)

A radioactive decay process where a neutron changes into a proton and a high-energy electron (beta particle). The proton remains in the nucleus while the electron is emitted, resulting in an unchanged atomic mass number and an increase of the atomic number by $1$ (e.g., carbon-14 decaying into nitrogen).

Gamma Decay ($\gamma$ Decay)

A process following alpha or beta decay where a nucleus rearranges itself and releases energy as gamma rays, causing no change to either the atomic mass number ($A$) or atomic number ($Z$).

Carbon Dating

A technique used to calculate the age of organic material by comparing the decaying amount of carbon-14 in a sample with the constant carbon-12 to carbon-14 ratio found in living organisms.

Radionuclide Therapy

The medical application of radioactive isotopes to treat health conditions such as hyperthyroidism, thyroid cancer, and blood disorders.

Nuclear Imaging Isotopes

Radioactive isotopes used in nuclear medicine to image physiological functions, including fluorine-18, gallium-67, krypton-81m, rubidium-82, nitrogen-13, technetium-99m, indium-111, iodine-123, xenon-133, and thallium-201.

Radiotherapy

A treatment for tumors that utilizes gamma radiation emitted from the cobalt-60 isotope.

Food Storage Treatment

The application of gamma radiation to fresh food to kill bacteria and extend shelf life, which remains controversial due to public concerns regarding long-term health effects.

Gamma Sterilisation

The process of sterilising surgical instruments and hospital dressings by exposing them to gamma radiation.