Which radioactive element with atomic number 43 in the modern periodic table is unstable, and the half-lives of all its isotopes are relatively short, from 4.2 million years to 5.0 s?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. Technetium.
- The radioactive element with atomic number 43 in the modern periodic table is Technetium (Tc).
- Technetium is indeed unstable, and all of its isotopes are radioactive.
- The half-lives of its isotopes vary widely, ranging from 4.2 million years to as short as 5.0 stable.