Algonquin College Health Program Assessment (AC-HPAT) Practice Exam

What does the term 'atomic weight' refer to?

1. The mass of an element's nucleus

2. The average mass of all isotopes of an element

3. The weight of a single atom

4. The number of neutrons in an isotope

The correct answer is: The average mass of all isotopes of an element

The term "atomic weight" refers to the average mass of all isotopes of an element, taking into account their relative abundances. This concept acknowledges that elements can exist in multiple forms known as isotopes, which have the same number of protons but different numbers of neutrons, leading to variation in their mass. The atomic weight provides a weighted average that reflects these variations rather than just focusing on one particular isotope. This average measurement is crucial in chemical calculations and understanding the properties of elements in a broader context, such as in stoichiometry and in comparing different elements. The other choices do not accurately capture the definition of atomic weight. The first option, regarding the mass of an element's nucleus, doesn't reflect the contribution of electrons and is too simplistic. The third choice, which states that atomic weight is the weight of a single atom, overlooks that atomic weight refers to an average that encompasses multiple isotopes. Finally, the fourth option connects atomic weight to the number of neutrons in an isotope, which is a related concept but does not encompass the entirety of what atomic weight represents.