Is radon-222 a radioactive decay product of radium-226 found in low concentrations in most rock and soil?

Radon-222 is indeed a radioactive decay product of radium-226, which is commonly found in various types of rocks and soils. The decay process originates with uranium-238, which decays into radium-226. From there, radium-226 undergoes further decay to produce radon-222 as one of its byproducts. This process contributes to the presence of radon-222 in the natural environment, although typically in low concentrations. The connection between radium-226 and radon-222 is significant in the study of radon, particularly concerning its health implications and the need for monitoring in residential and occupational settings. Therefore, the statement is true, reflecting an accurate understanding of these radioactive elements and their relationships.