Assessment And Qualifications Alliance (AQA) GCSE Chemistry Paper 1 Practice Exam

Relative atomic mass refers to the average mass of atoms of an element, taking into account the different isotopes of that element and their relative abundances. This value is a weighted average that reflects the occurrence of isotopes in nature rather than just the mass of a single atom. Isotopes are variants of an element that have the same number of protons but different numbers of neutrons; therefore, each isotope has a different mass. The relative atomic mass is calculated by considering the masses of these isotopes and the percentages in which they occur, which provides a more accurate representation of the element's mass as found in nature. The other options do not accurately convey the concept of relative atomic mass. While the mass of a single atom would only represent one specific isotope and not the average, the mass of protons focuses solely on the constituents of the nucleus and neglects the contribution of neutrons, which are also crucial to an atom's mass. Additionally, the mass of electrons is negligible compared to protons and neutrons, making the sum of all electron masses irrelevant in determining the overall atomic mass. Thus, option B is the most complete and accurate definition of relative atomic mass.