Question

question 51
which of the following isotopes has the longest half-life?
a iodine-131
b iron-59
c phosphorus-32
d cobalt-60

Explanation:

To determine which isotope has the longest half - life, we recall the half - lives of the given isotopes:

• Iodine - 131 has a half - life of about 8.02 days.
• Iron - 59 has a half - life of about 44.5 days.
• Phosphorus - 32 has a half - life of about 14.3 days.
• Cobalt - 60 has a half - life of about 5.27 years (which is much longer than the half - lives of the other three isotopes when converted to days).

By comparing these half - lives, we can see that Cobalt - 60 has the longest half - life among the given options.

Answer:

D. Cobalt - 60