Question

Which best describes a radioactive isotope?

Answer 1

I think its A because the nuclei of some isotopes are unstable and emit radiation.

Answer 2

Answer: Option (A) is the correct answer.

Explanation:

An isotope with an unstable nucleus which decomposes readily and results in the emission of radiation and a nuclear electron or helium nucleus achieves a stable nuclear composition is known as a radioactive isotope.

For example, $^{210}_{84}Po \rightarrow ^{4}_{2}He + ^{206}_{82}Pb$

Here isotope of polonium decomposes in order to achieve a stable nuclear composition.

Thus, we can conclude that an atom is unstable best describes a radioactive isotope.