Question

Which of the following is the correct sequence of the noble gases in their group in the periodic table
A. Ar, He, Kr, Ne, Rn, Xe
B. He, Ar, Ne, Kr, Xe, Rn
C. He, Ne, Ar, Kr, Xe, Rn
D. He, Ne, Kr, Ar, Xe, Rn

Answer 1

Hint: The periodic table was prepared based on the periodic law. The rows of the table are known as periods, and the columns are known as groups. Down the group, atomic mass increases.

Complete Step by Step Solution:
The periodic law expresses that the characteristics of the chemical elements show a frequent reliance on their atomic numbers. Elements from the same column group of the periodic table exhibit identical chemical properties.

One such group contains noble gases. This group is called Group-18 or zero groups. Noble gases are also called inert gases, aerogenes, etc. Down the group, atomic size increases due to the addition of electrons in subsequent subshells. There are six noble gases which are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and the radioactive radon (Rn).

The atomic mass of He, Ne, Ar, Kr, Xe, and Rn is 4u, 20u, 39u, 83u, 54u, and 86u respectively. So, the correct sequence of the noble gases in their group in the periodic table is He, Ne, Ar, Kr, Xe, and Rn.
So, option C is correct.

Note: Radon is documented as the second most recurring reason for lung cancer, after cigarette smoking. Yet, it also carries advantageous applications in radiotherapy, arthritis therapy, and bathing. In radiotherapy, radon has been utilised to treat cancers. Radon exposure might treat auto-immune diseases such as arthritis.