Short answers, pulled from the story.
Henri Becquerel discovered that uranium salts could blacken a photographic plate in 1896. This French physicist proved that invisible energy emanated from atoms without any external light source. His observation shattered the belief that atoms were immutable building blocks of matter.
Marie Curie and Pierre Curie isolated two new elements named polonium and radium from tons of uranium ore. They coined the term radioactivity to describe the emission of ionizing radiation by heavy elements. Their research on radium launched an era of using the substance for cancer treatment.
Three primary forms of invisible energy released by radioactive atoms exist and are named alpha, beta, and gamma rays. Alpha particles are helium nuclei stopped by paper, beta particles are high-speed electrons requiring aluminium shielding, and gamma rays are neutral electromagnetic radiation reduced by lead. These three types of decay are governed by different fundamental forces.
The half-life of carbon-14 is 5,730 years and is used to date organic matter. This statistical regularity allows scientists to use radioactive isotopes as precise clocks for measuring time spans. Uranium-238 has a half-life of 4.5 billion years and helps determine the age of the Earth.
The decay chain of neptunium-237 eventually produces stable lead-206. This process involves a series of alpha and beta decays where each daughter nuclide decays into another until stability is reached. The decay of primordial radionuclides like uranium and thorium contributes significantly to the Earth's internal heat budget.
The half-life of rhenium-187 reduced from 41.6 billion years to just 32.9 years when fully ionized. This bound-state beta decay challenges the assumption that decay rates are constant and unaffected by external conditions. Chemical environments can also slightly alter the decay rates of certain isotopes like beryllium-7.