Question

a. List the noble gas elements. Which of the noble gases has only radioactive isotopes? (This situation is indicated on most periodic tables by parentheses around the mass of the element. See inside front cover.) b. Which lanthanide element has only radioactive isotopes?

Short answer

a) The noble gas elements are He, Ne, Ar, Kr, Xe, and Rn. Radon (Rn) has only radioactive isotopes. b) Among the lanthanide elements, promethium (Pm) has only radioactive isotopes.

Step-by-step solution

Locate the noble gases on the periodic table

The noble gases can be found in Group 18 of the periodic table (the last column on the far right).

List the noble gas elements

The noble gas elements are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn).

Determine which noble gas has only radioactive isotopes

Check the periodic table for the indication of radioactive isotopes. The element with parentheses around the mass is considered having only radioactive isotopes. In this case, it is radon (Rn). a) The noble gas elements are He, Ne, Ar, Kr, Xe, and Rn. Radon (Rn) has only radioactive isotopes. b) Identifying the lanthanide element with only radioactive isotopes

Locate the lanthanide elements on the periodic table

The lanthanide elements can be found in the f-block of the periodic table, which is usually located as a separate row below the main body of the table.

Identify the element among the lanthanides with only radioactive isotopes

Check for parentheses around the mass of the lanthanide elements on the periodic table. The element with parentheses around the mass has only radioactive isotopes. In this case, it is promethium (Pm). b) Among the lanthanide elements, promethium (Pm) has only radioactive isotopes.