ASNT Industrial Radiography Radiation Safety Practice Test

An element's weight is determined by its:

1. Z number

2. Atomic radius

3. Electronegativity

4. Mass number

The correct answer is: Z number

The mass of an element is primarily determined by its mass number, which is the sum of the protons and neutrons in its nucleus. The mass number reflects the total number of these nucleons, which are the particles that contribute significantly to the mass of the atom. The Z number, also known as the atomic number, represents the number of protons in an atom and defines the element itself. While it is crucial for identifying the element and determining its place on the periodic table, it does not directly indicate weight. In contrast, the mass number incorporates both protons and neutrons, offering a direct measurement related to the element’s overall weight. In summary, the correct answer highlights that while the Z number identifies the element, the actual weight is more accurately reflected through the mass number, which includes the neutrons that also contribute to the total atomic mass.