Charge signs in atomic particles: By convention, which particles carry the negative and positive electric charge, respectively (in that order)?

Introduction / Context:
Charge sign conventions underpin circuit theory and particle physics. Correctly assigning negative and positive charges is essential for understanding current direction, electric fields, and chemical bonding.

Given Data / Assumptions:

• Elementary particles considered: electron, proton, neutron.
• Conventional current direction is from positive to negative terminal, opposite to electron flow.

Concept / Approach:
Electrons carry a single negative elementary charge, while protons carry a single positive elementary charge. Neutrons are electrically neutral. The atom as a whole may be neutral or an ion depending on electron count, but charge signs belong to the particles themselves.

Step-by-Step Solution:
Identify the negative charge carrier among fundamental particles: electron.Identify the positive charge carrier: proton.Match the required order: negative then positive.

Verification / Alternative check:
Electrostatics experiments and mass spectrometry both confirm the charges of electrons and protons; neutron has no net charge.

Why Other Options Are Wrong:

• Proton and electron: order reversed relative to the question.
• Atom and nucleus / electron and element: categories are mismatched; element is not a particle.
• Neutron and proton: neutron is neutral, not negative.

Common Pitfalls:
Confusing conventional current direction with electron flow direction.

Final Answer:
Electron and proton