Question

Which is the radioactive isotope of hydrogen?
A. \[_1{H^1}\]
B. \[_1{H^2}\]
C. \[_1{H^3}\]
D. All of these

Answer 1

Hint: Try to recall that radioactive isotope is an isotope of an atomic element that has a non-standard number of neutrons. Now, by using this you can easily find the correct option from the given ones.
Complete step by step solution:
1) It is known to you that isotopes of an element have the same atomic number but different mass numbers. In other words, the number of protons and electrons remains the same but the number of neutrons is different. Radioactive isotopes are also known as radioisotopes or radionuclides.
2) In radioisotopes, the nucleus has high energy which makes it unstable. To attain the stability the atom emits energy in the form of gamma radiation or alpha and beta particles. This process is called radioactive decay.
3) It is known to that hydrogen occurs in three forms which are as follows:

Protium- The chemical symbol of protium is \[_1{H^1}\]. It has one electron, one proton and does not contain any neutron.
Deuterium- The chemical symbol of deuterium is \[_1{H^2}\]. It has one one electron, one proton and one neutron.
Tritium- The chemical symbol of tritium is \[_1{H^3}\]. It has one electron, one proton and two neutrons in it.

Since, the number of neutrons is greater than the number of protons in tritium which makes the nucleus unstable, so tritium is the radioactive isotope of hydrogen and it will undergo radioactive decay.

Therefore, from above we can say that option C is the correct option to the given question.

Note: It should be remembered to you that tritium is used as a boosting agent in the centre of a thermonuclear bomb. It allows for greater efficiency in the initiation fission portion of thermonuclear explosion. The advantage is that you get the same size explosion, with half the plutonium. This was very important back in the early days of U.S.’s nuclear arms buildup.