Question

Tritium emits:
 $ (i){\text{ }}\alpha {\text{ - }} $ particle
 $ (ii){\text{ }} $ Positron
 $ (iii){\text{ }}\beta {\text{ - }} $ particle
 $ (iv){\text{ }} $ Neutron

Answer 1

Hint: There are three isotopes of hydrogen atoms which are protium, deuterium and tritium. Out of these isotopes tritium is a radio-active element. Protium and deuterium do not decay while tritium decays. Thus we regard tritium as a radioactive isotope of hydrogen.

Complete answer:
Since we know that there are three isotopes of hydrogen which are present in nature. One is protium which has a single proton and single electron, thus having no neutron. Another one is deuterium which comprises one electron, one proton and one neutron. Its atomic mass number is two. Tritium is another isotope of hydrogen atoms which is radioactive in nature. It comprises one electron, one proton but having two neutrons. The mass number of tritium is three. Since it is a radioactive element therefore it decays gradually. It decays through $ \beta - $ particle emission . its decay can be represented as,
 $ H_1^3{\text{ }} \to {\text{ He}}_2^3{\text{ + e}}_{ - 1}^0{\text{ + }}\nu _0^0 $
Here $ \nu _0^0 $ is known as an anti-neutrino particle and $ {\text{e}}_{ - 1}^0 $ is the $ \beta - $ particle or we can say it is an electron emission. Therefore we can say that tritium emits $ \beta - $ particle. Other isotopes of hydrogen atoms are not radioactive in nature.
Hence the correct option is $ (iii){\text{ }}\beta {\text{ - }} $ particle.

Note:
 The mass number of any element is the sum of the number of protons and neutrons. Since tritium contains two neutrons and one electron, thus its atomic mass number is three. Also it contains more neutrons than the number of protons, that’s why it is a radioactive element. There are other ways of emission like emission of alpha particles and more. But in $ \beta - $ particle an electron is emitted.