Question

Atomic number of Radon is:
(a)- 54
(b)- 86
(c)- 72
(d)- 68

Answer 1

Hint: Radon is an element that belongs to group 18 of p-block which is also known as the noble gas group. It is the last element of this group and comes in the 6th period. Since it is a noble gas its octet is complete.

Complete step by step answer:
Radon is an element which is placed in the last group of the periodic table i.e., group 18 of the p-block. It is a noble gas and belongs to the noble gas group. Its symbol is Rn. The electronic configuration is given below:
$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{10}4s^{2}4p^{6}4d^{10}4f^{14}5s^{2}5p^{6}5d^{10}6s^{2}6p^6$
So its atomic number is 86 and atomic mass of radon is $222\text{ g/mol}$.
Since it is a member of noble gas which means that it has complete octet and it would be difficult to remove an electron from its outer shell, hence its ionization enthalpy is $1037\text{ kJ/mol}$.
The electron gain enthalpy of radon is $68\text{ kJ/mol}$ which is very low because it has a very low tendency to add an electron.
The density of radon is $9.7\text{ x 1}{\text{0}}^{-3}\text{ g/c}{\text{m}}^3$.
It has very low melting and boiling points which are 202 and 211 K respectively.
Since it is the last element of the noble gas group, it is a radioactive element, therefore it is present in a very minute quantity. It is available in isotope form and its most stable isotope is ${}^{222}Rn$ having a half-life period of 3.8 days only.

Therefore, the correct answer is an option (b)- 86.

Note: Radon is used in the medical field, where it can be used for killing the cancerous cells. But long exposure to radon causes diseases like arthritis. Later the carcinogenic nature of radon became apparent.