Particle Physics – Relative Mass Scales Which ordering lists the rest masses of the three elementary particle families in decreasing order (heaviest to lightest)?

Introduction / Context:
In high-energy physics, hadrons (baryons and mesons) are composite particles built from quarks, while leptons (such as electrons and neutrinos) are elementary and generally lighter. Knowing typical mass scales helps you quickly sanity-check reaction energetics and decay possibilities.

Given Data / Assumptions:

• Baryons are three-quark hadrons (e.g., proton, neutron).
• Mesons are quark–antiquark pairs (e.g., pion, kaon).
• Leptons include electron, muon, tau, and neutrinos.

Concept / Approach:
Typical masses: baryons are around 1 GeV/c^2 (proton 938 MeV/c^2); light mesons such as pions are ~140 MeV/c^2; electrons are ~0.511 MeV/c^2, and neutrinos are far lighter. Although some heavy mesons (charmonium, bottomonium) exceed proton mass, the standard comparative order taught in introductory courses is baryons > mesons > leptons for representative species.

Step-by-Step Solution:

Verification / Alternative check:
Cross-check with decay kinematics: baryons can decay into mesons and leptons when allowed; mesons frequently decay into lepton pairs, consistent with mass hierarchies.

Why Other Options Are Wrong:

• Leptons first: contradicts typical mass scales (electron and neutrinos are light).
• Mesons first: lighter than baryons in standard examples.
• Disordered listings mix heavy and light families incorrectly.

Common Pitfalls:
Overgeneralising from heavy mesons (e.g., B mesons) that can exceed proton mass. The question concerns the broad, representative trend taught at entry level.

Final Answer:
Baryons, Mesons, Leptons