To determine the nuclear radius of ‌125‌Fe, we need to use the relationship between nuclear radius and mass number. The nuclear radius (R) of a nucleus is given by the empirical formula: R=R0A1∕3 where: R0 is the proportionality constant (approximately 1.2−1.3 fermi) and A is the mass number (number of nucleons). Given the nuclear radius of ‌27‌Al (Aluminium-27) is 3.6 fermi, we can use this to find R0 : R27‌Al=R0⋅271∕3 We know:
=1.2‌ fermi ‌ Now, using this R0, we find the radius of ‌125‌Fe (Iron-125): R125‌Fe=R0⋅1251∕3 Substitute R0 : R125‌Fe=1.2⋅1251∕3 We need to find 1251∕3 : 1251∕3=5 Therefore: R125‌Fe=1.2⋅5=6‌ fermi ‌ Converting fermi to meters (since 1 fermi =10−15 meters): 6‌ fermi ‌=6×10−15‌ meters ‌ The correct option is: Option C 6×10−15m