Explanation:
To find the isotope that is expected to be radioactive we have to compare the given isotopes with the ones that we find the in the periodic table.
(A) Ti:
Isotope ----> atomic mass = 48 atomic number = 22
Periodic table ---> average atomic mass = 47.9 atomic number = 22
(B) Sr:
Isotope ----> atomic mass = 88 atomic number = 38
Periodic table ---> average atomic mass = 87.6 atomic number = 38
(C) Os:
Isotope ----> atomic mass = 192 atomic number = 76
Periodic table ---> average atomic mass = 190.2 atomic number = 76
(D) Pu:
Isotope ----> atomic mass = 244 atomic number = 94
Periodic table ---> average atomic mass = 244 atomic number = 94
If we take a look at them we will see that the only one that is different is osmium. The atomic mass of the isotope is 192 amu, that means that this isotope has 2 more neutrons than the average atom of the element. So we can expect that it could be radioactive.
Answer: C. Os
