Which produces barium-137 when it undergoes gamma decay? A. Cesium-137 B. Cesium-138 C. Barium-137 D. Barium-138

C. Barium-137

Explanation:

We have barium-137

Required to identify the radioisotope that undergoes gamma decay to produce Ba-137.

We need to know that when a radioisotope undergoes gamma decay its mass number and the atomic number remains unchanged.

The atomic number of Ba-137 is 56 while the mass number is 137. We need to identify the choice whose atomic number is 56 and mass number is 137.

In this case,

Cesium-137 has a mass number 137 and atomic number 55 Cesium-138 has a mass number 138 and atomic number 55 Barium-137, has a mass number, 137 and atomic number 56. Barium-138 has a mass number 138 and atomic number 56

Therefore the correct choice is C. Barium-137