AS Level Chemistry Practice Exam 2025 – The Comprehensive All-In-One Guide to Achieve Exam Success!

The relative masses of protons, neutrons, and electrons are fundamental concepts in atomic structure. Protons and neutrons have essentially the same mass, which is approximately 1 amu (atomic mass unit). In contrast, the mass of an electron is significantly smaller, approximately 1/2000 of the mass of a proton or neutron. This difference in mass is critical for understanding atomic structure because it explains why protons and neutrons, located in the nucleus, contribute most of the atom's mass, while electrons, which occupy the space around the nucleus, contribute negligibly to the total mass.

Choosing the option that states the relative masses as 1 for protons, 1 for neutrons, and 1/2000 for electrons accurately reflects these values and highlights the considerable difference in mass between electrons and the nucleons (protons and neutrons). As such, the choice provided aligns with accepted scientific knowledge in chemistry regarding atomic structure.