What is invection or the definition

Asample of radium-226 will decay 1/4 of its original amount after 3200years. what is the half-life of radium-226?

The picture represents the process that produces most of the energy used by living organisms on earth. which process is represented in the picture? a) the magnetic attraction between two hydrogen nuclei. b) the fusion of hydrogen nuclei to produce a helium nucleus in the core of the sun. c) the fission of hydrogen nuclei to produce a helium nucleus in the core of the sun. d) the chemical reaction between hydrogen nuclei to produce a helium nucleus in earth's atmosphere.

Which is an example of a highly unstable isotope that is often used in fission reactions?