Answer:
Radium (Ra)
Step-by-step explanation:
The nuclear fuel at Chernobyl was uranium-235. However, one of the decay products of uranium-235 is radium.
Radium is chemically similar to calcium since it has two valence electrons and is the heaviest and last member of group 2.
Owing to its chemical similarity to calcium, it was able to replace calcium in people's teeth and bones. Radium is radioactive, the half life of Ra-226 is about 1602 years.
Other elements of group 2 are; beryllium, magnesium, strontium and barium.