Which component makes each amino acid unique

With the word calcite wich completes the analogy mineral, erosion, marble, or aragonite

Ihave no idea how to solve these. plus there's another question that is 2) a 10 kilogram meteorite is collected in space and brought back to earth. it is composed of 1.25 kg of uranium-238 and 8.75 kg of lead-206. how many u-238 half lives have passed? what is the approximate age of the meteorite?

Which particle controls what element an atom is?