Which is the best predictor of the radioactive nature of an isotope?
(a) the proton-to-electron ratio
(b) the neutron-to-proton ratio
(c) the neutron-to-electron
(d) ratio the electron-to-proton ratio

the neutron-to-proton ratio

Choice B is correct

Explanation:

An Isotope of an element refers to a form of the element whose nucleus has a given number of neutrons together with the number of protons which identifies the element uniquely. All the element of the periodic table have at least one isotope.

Some isotopes of some given elements have unstable nucleus and thus they emit ionizing radiation, also called radioactivity. An example of a radioactive isotope is Carbon-14 which is a radioisotope of the element carbon.

Thus it is the nucleus of an isotope that predicts its radioactive nature. The nucleus consists of neutron and protons.

B. the neutron-to-proton ratio

Explanation:

4d^55s^1 ( third choice)