What is a radioactive, colorless, odorless, tasteless noble gas that occurs naturally as the decay of radium?

Radon is the correct answer because it is recognized as a naturally occurring radioactive noble gas that results from the decay of radium. This process takes place deep within the earth, particularly in areas where uranium and radium are present in the soil and rocks.

Radon is unique among noble gases due to its radioactive properties, which differentiate it from other noble gases that are inert and non-reactive. Importantly, radon is colorless, odorless, and tasteless, making it difficult to detect without specialized equipment. It is crucial to note that radon can accumulate in buildings, particularly in enclosed spaces such as basements, posing health risks due to its radiation.

The other options do not accurately describe radon. The mention of lead paint refers to a different substance and involves lead rather than radon. The term "natural gas" typically denotes methane and does not include noble gases like radon. Therefore, the characteristics and origins of radon confirm its correctness as the answer to the question posed.