Question

Natural radioactivity was discovered by
a) Marie Curie
b) Ernest Rutherford
c) Henri Becquerel
d) Enrico Fermi

Answer 1

Hint: It is a property of atoms and nuclei. It is a spontaneous process. It exists in a periodic table whose atomic number is greater than 82. It is highly penetrating. Materials which do possess spontaneous emission of radiation are all natural radioactivity.

Complete step by step solution:
In periodic table, a scientist discovered that heavy element like uranium, radium having atomic number greater than 82 i.e. A > 82 are unstable and it is emitting highly penetrating radiation. And this kind of substance is called radioactive substances.

The phenomenon of spontaneous emission of radiations from radioactive substances is called radioactivity. This is all Natural radioactivity.
It is actually a property of atoms and nuclei. Therefore on the nano level also it is not affected by chemical or physical changes. Radioactivity, basically, is a nuclear phenomenon in which an unstable nucleus undergoes a decay. Such a kind of decay is called radioactive decay.
There are three kind of decay -

1. $\alpha$ decay in which helium nucleus $He_{2}^{4}$ is emitted.
2. $\beta$ decay in which electron or positron are emitted
3. $\gamma$decay in which high energy photons are emitted.
Correct option is C.

Note: Uranium, radium are the most common radioactive substances. You will not find this kind of substance in daily life. Its nuclei continuously goes under decay. There is also Radioactive Decay law.
Marie Curie radioactive elements polonium and radium while working with the mineral pitchblende. She also championed the development of X-rays.
Rutherford postulated the nuclear structure of the atom, discovered alpha and beta rays, and proposed the laws of radioactive decay.
Enrico Fermi built the first nuclear reactor.