Dr. Tsubokura's Radiation Lecture Vol.77

Author: Masaharu Tsubokura

Editors: Akihiko Ozaki M.D., Yuki Senoo

153. There are dozens of types of cesium

All materials are composed of small particles called protons, neutrons, and electrons. The number after the name of radioactive substances, as in cesium 134 and 137, indicates the sum of protons and neutrons. The nature of a substance varies depending on the balance of these numbers of particles. Radioactive substances have unbalanced numbers of particles, and they emit excessive protons, neutrons, electrons, and energy to stabilize themselves. These emitted substances are called radiation.

Furthermore, names of radioactive substances, such as cesium and uranium, are determined by the number of protons contained in their cores. That is to say, the substance named cesium always contains 55 protons.

There are several types of cesium containing various numbers of neutrons. For example, when a cesium core contains 60 or 90 neutrons, those substances are called cesium 115 and 145, respectively. Similarly to cesium 134 and 137, which are of critical concern to our daily lives, cesium 115 and 145 also emit radiation, as they contain unbalanced numbers of particles.