Question

An atom of radium combines with two atoms of chlorine to form $\text{RaC}{{\text{l}}_{2}}$ molecule. The radioactivity of $\text{RaC}{{\text{l}}_{2}}$ will be:
(a) Zero
(b) One- half of the same quantity of Ra
(c) One- third of the same quantity of Ra
(d) As much as that of the same quantity of Ra

Answer 1

Hint: Radioactivity is due to the instability in the nucleus of the atom and as result, it emits radiation and Ra is a radioactive element. Now answer the statement.

Complete step by step answer:
- Radium belongs to the category of alkaline earth metal which has the atomic number as 88 and is a radioactive metal (i.e. the metal in which the energy is produced by breaking up atoms) and thus, the element radium is used as a source of radiation. On the other hand, chlorine is a halogen belonging to the category of halogens having the atomic number as 17and is non-radioactive.
- By the term radioactivity we mean, the emission of radiations by certain atoms due to the disintegration of the nucleus i.e. breakdown of the nucleus, and in turn thus emits out the energy in the form of radiations. This disintegration of the nucleus is mainly due to the instability of the nucleus and the instability in the nucleus is mainly due to the presence of neutrons and protons in the nucleus. Thus, we can say that radioactivity occurs because some atoms have unstable nuclei. And the nuclear 'decay' takes place when the nucleus rearranges itself in order to become more stable, and thus, at the same time it gives out energy in the form of radiations.
- We know that in an atom, the protons( positively charged particles) and the neutrons(neutral molecules i.e. neither having positive nor the negative charge on them ) are packed together in the small space inside the nucleus and there must be some force of attraction in between these particles( i.e. the neutrons and the electrons) to maintain the existence of nucleus. But the force of attraction between these particles i.e. the neutrons and the protons is not sufficient to hold these particles together in such a small space, but the repulsion force of attraction between the protons (positively charged) makes the nucleus very unstable and thus the nucleus breaks and emits radiations.
- Since we know that the nuclear forces operate only within a small distance i.e. around 0.10 fermi only, so thus, those nuclei which are having the n/p ratio as one, are highly stable and the elements with a high n/p ratio are very unstable in nature and thus are radioactive.
- Elements till atomic number 20 are stable with an n/p ratio of 1, and as the atomic number increases, the n/p ratio increases, and thus the stability decreases i.e. instability increases.
- Since the radioactivity occurs due to the unstable nucleus, so the radioactivity of $\text{RaC}{{\text{l}}_{2}}$ will remain the same as that of the Ra because out of $\text{RaC}{{\text{l}}_{2}}$, only Ra is radioactive and not the halogen Cl.
So, the correct answer is “Option D”.

Note: Protons being positively placed together inside the nucleus, repels each other and the force of repulsions between the proton-proton are responsible for the instability of the nucleus.