The reason is that energy and frequency of a gamma ray which is emitted by a radioactive element, is far beyond that of the radio band of electromagnetic spectrum! Every nucleus contains neutrons as well as protons.
Neutrons are neither positively charged, nor negatively charged, they are neutral particles. As you might remember from high school physics, like charges repel each other while unlike charges attract each other.
Early gold discoveries in Australia were kept quiet as many feared a gold rush would plunge the largely convict population into chaos and lawlessness.
However the rush to California depleted the new colony’s small population and forced the authorities to think differently about Australian gold.
Radioactive isotopes have a variety of applications.
(Recall that tritium, H, is a radioactive isotope of hydrogen.) Tracers can also be used to follow the steps of a complex chemical reaction.
This Buzzle article has a list of radioactive elements that abound in nature, arranged in the order of increasing atomic number, along with their decay modes. Radioactivity arrived on the scene of world physics in the 19th century, just when people thought they knew everything in physics.
With its discovery in 1896, radioactivity opened up a Pandora's box of questions and revealed a new world, waiting to be explored in the microcosm of the atomic nucleus. Radioactivity is a very interesting phenomenon in nature.
Alpha decay typically occurs in nuclei that are so big that they can’t be stable.
In alpha decay, the nucleus ejects a helium nucleus (alpha particle) composed of two neutrons and two protons, dropping the mass of the original nucleus by four mass units.