Atomic structure and charge — definition of a negative ion: Which description correctly defines a negative ion (anion) in terms of its subatomic particle counts?

Introduction / Context:
Ions are atoms with a net electric charge due to a difference between the number of protons (positive charges) and electrons (negative charges). Understanding the sign of that charge is foundational for chemistry, solid-state physics, and semiconductor device theory.

Given Data / Assumptions:

• Protons carry +1 elementary charge each; electrons carry −1 elementary charge each; neutrons are neutral.
• “Negative ion” (anion) implies total negative net charge.
• We compare particle counts to infer the sign of net charge.

Concept / Approach:
Net charge Q is proportional to (number of protons − number of electrons). If an atom has more electrons than protons, the net charge is negative, and the atom is a negative ion. Neutrons do not affect the sign of charge, only the mass and isotopic identity.

Step-by-Step Solution:
Identify the key comparison: electrons vs protons.If electrons > protons → net charge negative → negative ion (anion).Therefore, the correct statement is “more electrons than protons.”

Verification / Alternative check:
Consider neutral atoms: electrons = protons. Adding one electron (without changing protons) yields a net −1 charge, creating a negative ion. This matches the definition.

Why Other Options Are Wrong:
(a) and (b) compare with neutrons, which do not determine charge. (d) Describes a positive ion (cation). (e) Invalid because a correct option exists.

Common Pitfalls:
Confusing particle roles (neutrons vs electrons); thinking mass differences affect charge; forgetting that charge is about proton–electron balance.

Final Answer:
An atom that contains more electrons than protons.