Question

Radioactivity is due to:
(A) Stable electronic configuration
(B) Unstable electronic configuration
(C) Stable nucleus
(D) Unstable nucleus

Answer 1

Hint: We must already know that radioactivity is a process by which unstable nuclei lose energy in the form of radiation. The most common types of radiation include alpha, beta and gamma radiation.

Complete step by step solution:
The term radioactivity was actually coined by Marie Curie. They extracted Uranium from its ore and found out that the leftover ore showed more radioactivity than pure uranium. Thus they concluded that the ore must have had other radioactive elements derived from Uranium. This ultimately led to the birth of Polonium and Radium.
This radioactivity arises due to intense internal conflict in the nucleus hence many isotopes of certain elements are unstable and emit radiation. An unstable nucleus decays spontaneously into a more stable configuration by emitting certain subatomic particles and electromagnetic energy. Sometimes, fission fragments, neutrons and protons are also emitted.
Majority of all nuclei found on earth are stable. Only about 50 naturally occurring isotopes are known to be radioactive till date. Radioactive decay usually changes one nucleus to another if the product nucleus has a greater nuclear binding energy than the reactant nucleus. The probability that a particular nucleus will undergo radioactive decay during a fixed length of time does not depend on the age of the nucleus or how it was created.
The number of nuclei in a sample that will decay in a given interval of time is proportional to the number of nuclei in the sample.
 
Hence, the correct answer is Option (D) unstable nucleus.

Note: We should remember that usually heavy elements are radioactive. The study of radioactivity is essential to understand the structure of the earth because radioactive decay heats the earth’s interior to very high temperatures.