Radiation Safety Practice Exam

What type of chemical element is cesium-137?

1. A metal

2. An alkaline earth metal

3. An alkali metal

4. A transition metal

The correct answer is: An alkali metal

Cesium-137 is classified as an alkali metal. Alkali metals are found in Group 1 of the periodic table and are characterized by having one electron in their outermost shell, which makes them highly reactive and capable of easily forming positive ions. Cesium, with the atomic number 55, exhibits typical properties of this group, including a low melting point and a tendency to react vigorously with water. Its status as a radioactive isotope of cesium adds to its significance, particularly in radiation safety contexts. Cesium-137 is commonly used in medical applications, such as radiotherapy and in industrial gauges, due to its ability to emit gamma radiation, which can be useful in certain applications but also requires careful handling due to its radioactive nature. Thus, classifying cesium-137 as an alkali metal is accurate because it aligns with its group placement in the periodic table and its physical and chemical properties.