Question

Radioactive halogen is:
(A) I
(B) At
(C) Po
(D) Br

Answer 1

Hint: Halogens is the common name for the six elements present in Group 17 of the periodic table which contains fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (As), and tennessine (Ts). Though, nothing much is known about the last two elements.

Complete step by step solution:
Due to their high reactivity, the free halogen elements are not found in nature. They are generally found in combined form, with fluorine being the most abundant of the halogens present in the Earth’s crust. But Astatine and tennessine go even further, they do not even occur naturally. They consist of only short-lived radioactive isotopes, which gives its name derived from Greek word astatos, meaning “unstable.” Astatine was synthesized by Corson in 1940 and others at the University of California. It is produced by bombarding targets made of bismuth-209 with high energy alpha particles (helium nuclei). Astatine-211 is the result and has a half-life of 7.2 hours. The most stable isotope of astatine is 210, having a half-life of 8.1 hours.
There’s nothing much known about the chemical properties of astatine but it is expected to follow the trends like the other halogens, although much less vigorously, and it should be more metallic than iodine.
So, the correct option is (b).
Note: Mendeleyev also predicted this unknown element as eka-iodine due to its position directly below iodine in the halogen group of elements. There is less than 30 grams of astatine in the Earth's crust.