No. The most common isotope(s) of an element are often stable.
There is no group specified so it is not possible to be sure about this answer but all isotopes of promethium are radioactive.
An example is uranium.
Pm is Prometheum. All isotopes of this element are radioactive.
All the isotopes of uranium are radioactive and unstable.
Yes. There are no stable isotopes of astatine, they are all radioactive.
Frederick Soddy in 1912 observed first radioactive isotopes and J.J. Thomson first stable isotopes in1913.
All the isotopes of nobelium are radioactive and unstable.
No, Barium has both stable and radioactive isotopes. Out of its 25 known isotopes, only 6 of them are considered radioactive. The most stable isotope of Barium is Barium-138, which is not radioactive.
Technetium (Tc) is the element that has no stable isotopes. All of its isotopes are radioactive with half-lives ranging from minutes to millions of years.
All or almost all elements have radioactive isotopes if artificial isotopes are included. Among the naturally occurring elements, uranium, polonium, radium, and thorium have naturally occurring radioactive isotopes on earth.
Promethium, Technetium, and any element heavier than Bismuth.
Technetium, Promethium, and all elements heavier then Bismuth.