ASNT Industrial Radiography Radiation Safety Practice Test

What does the term 'radioactive' specifically indicate about an atom?

1. It has a stable nucleus

2. It is in a gaseous form

3. It is unstable and excessive energy

4. It is a single element

The correct answer is: It is unstable and excessive energy

The term 'radioactive' specifically indicates that an atom is unstable and has excessive energy. Radioactive atoms undergo a process known as radioactive decay, where they emit radiation in the form of particles or electromagnetic waves in an effort to reach a more stable nuclear state. This instability is due to an imbalance in the number of protons and neutrons in the nucleus, leading to the emission of energy as the atom transforms into a different element or isotopic form. The emitted radiation might include alpha particles, beta particles, or gamma rays, reflecting the atom's quest for stability. This characteristic is fundamental in various applications, including radiography, where the energy emitted is utilized for imaging purposes.