Difficult# Calculation: Half-Life of Iodine-131

CHEM-W78YF6

Iodine-131 ($_{ }^{131}{I}$) is a radioisotope frequently used to treat thyroid cancer. The half-life of $_{ }^{131}{I}$ is 8.0 days.

What mass, in mg, of $_{ }^{131}{I}$ is left from an original sample of 270 mg of $K_{ }^{131}{I}{O}_{3}$ after 26.0 days?

Assume the atomic mass of $_{ }^{131}{I}$ is 131.0, K is 39.1, and O is 16.0.