Some substances emit radiation without any need to expose the material to other energy sources. We call these substances
A) naturally radioactive.
B) noble gases.
C) rotationally symmetric.
D) thermal equilibrium.

Question

Quizplus · Accepted Answer

Naturally radioactive substances have unstable atomic nuclei that spontaneously emit radiation in order to reach a more stable state. This process is known as radioactive decay. Examples of naturally radioactive substances include uranium, radium, and carbon-14.

Some Substances Emit Radiation Without Any Need to Expose the Material