An element's weight is represented by which term?

The correct term that represents an element's weight is atomic weight. Atomic weight refers to the average mass of an element's atoms, taking into account the relative abundance of the different isotopes that exist for that element. It is typically expressed in atomic mass units (amu).

The other options do not accurately describe an element's weight. The atom number, also known as the atomic number, refers to the number of protons in the nucleus of an atom, which determines the element's identity and position on the periodic table. The Z number is a terminology that may sometimes informally refer to the atomic number, but it does not relate to an element's weight. Molecular weight, on the other hand, pertains to the weight of a molecule composed of two or more atoms and is not related to the weight of individual elements. Thus, atomic weight is the most accurate term for indicating an element's weight.