Question

What periodic table elements are radioactive?

Answer 1

As we know very well that Radioactive elements are constituent of atoms whose nuclei are unstable i.e. always be dynamic and give off atomic radiation as part of a process of attaining stability. Since the emission of radiation transforms radioactive atoms into another chemical element, which may be stable(non dynamic) or may be radioactive such that it undergoes further decay.

Complete step by step answer:
According to the modern periodic table given by Mosley. There are 34 radioactive elements. They either have no stable naturally occurring isotope, or else are entirely artificial as all artificial elements have no stable isotopes(same atomic number , different atomic masses)
These are as follows
Hydrogen (H)
Beryllium (Be)
Carbon (C)
Calcium (Ca)
Iron (Fe)
Cobalt (Co) (Synthetic)
Nickel (Ni)
Zinc (Zn) (Synthetic)
Selenium (Se)
Krypton (Kr)
Rubidium (Rb)
Strontium (Sr)
Yttrium (Y)
Zirconium (Zr)
Niobium (Nb) (Metastable)
Molybdenum (Mo)
Technetium (Tc)
Ruthenium (Ru)
Ruthenium(Ru)
Palladium (Pd)
Silver (Ag)
Tin (Sn)
Antimony (Sb)
Tellurium (Te)
Tellurium (Te)
Iodine (I)
Xenon (Xe)
Cesium (Cs)
Promethium (Pm)
Europium (Eu)
Iridium (Ir) (Synthetic)
Iridium (Ir) (Synthetic, Metastable)
Bismuth (Bi)
Polonium (Po)

Note: In all of these radioactive Elements some of the elements are only synthetic some only come under meta stable state and some of them are both synthetic and metastable. Their symbols are also mentioned after their name in the above answer.