Such unstable nucleus emitted some radiations and convert in to some other stable nucleus and known as radioactive elements. Generally these radiations consist some particles like alpha and beta particle in some time charge less gamma rays emitted.Generally, elements with atomic number more than 82 show radioactivity and disintegrated to small nuclei with the emission of alpha, beta, proton, neutron particles or gamma rays.He believed all metals were based on mercury mixed in different proportions and different purities with sulfur.If the mercury and sulfur were perfectly pure and mixed in perfect proportions, they would form gold.This is because both the protons and the neutrons in an atom have a relatively equal mass.The mass of an electron is so insignificant that it is not represented in the atomic mass.Out of these three particles, protons and neutrons located at the center of the atom as a hard and dense part known as nucleus.
Atoms become unstable due to large neutron to proton ratio.
Uranium-238 decays by alpha emission into thorium-234, which itself decays by beta emission to protactinium-234, which decays by beta emission to uranium-234, and so on.
The various decay products, (sometimes referred to as “progeny” or “daughters”) form a series starting at uranium-238.
Uranium is the principal fuel for nuclear reactors and the main raw material for nuclear weapons.
Natural uranium consists of three isotopes: uranium-238, uranium-235, and uranium-234. The nuclei of radioactive elements are unstable, meaning they are transformed into other elements, typically by emitting particles (and sometimes by absorbing particles).
Mercury or quicksilver has been known since ancient times. Mercury was known to the ancient Chinese, Egyptians and Hindus and has been found in Egyptian tombs dating back to about 1500 B. The Romans modified the Greek name slightly, referring to mercury as Hydragyrum, from which we get mercury’s modern chemical symbol Hg.