Who discovered radiometric dating?

Answer 1

Take a look at this:

"In 1896 Henri Becquerel and Marie Curie discovered that certain isotopes undergo spontaneous radioactive decay, transforming into new isotopes. Atoms of a parent radioactive isotope randomly decay into a daughter isotope. Over time the number of parent atoms decreases and the number of daughter atoms increases. Rutherford and Soddy (1902) discovered that the rate of decay of a radioactive isotope depends on the amount of the parent isotope remaining. Later it was found that half of the parent atoms occurring in a sample at any time will decay into daughter atoms in a characteristic time called the half-life."

from http://myweb.cwpost.liu.edu/vdivener/notes/radiometric_dating.htm

These discoveries lead to the practical application of radiometric dating so you could probably credit the discovery to these individuals.