Isotope(s) of hydrogen which emits low energy $$\beta^-$$ particles with $$t_{1/2}$$ value > 12 years is/are

Hydrogen has three isotopes: protium ($$^1\text{H}$$), deuterium ($$^2\text{H}$$), and tritium ($$^3\text{H}$$). Among these, protium and deuterium are stable and non-radioactive, so they do not emit any radioactive particles.

Tritium ($$^3\text{H}$$) is radioactive. It undergoes $$\beta^-$$ decay: $$^3_1\text{H} \to \, ^3_2\text{He} + \beta^- + \bar{\nu}_e$$. The $$\beta^-$$ particles emitted by tritium have a very low maximum energy of about 18.6 keV, making them low-energy $$\beta^-$$ emitters. The half-life of tritium is approximately 12.3 years, which is greater than 12 years.

Therefore, the isotope of hydrogen that emits low-energy $$\beta^-$$ particles with a half-life greater than 12 years is tritium.

The answer is option (2).