Definition check in basic atomic structure: the atomic number (Z) of an element equals the number of which fundamental particle in the atom?

Introduction / Context:
The atomic number Z uniquely identifies a chemical element on the periodic table. Distinguishing among protons, neutrons, and electrons clarifies how elements differ and how ions form without changing elemental identity.

Given Data / Assumptions:

• Neutral atoms have electrons equal to protons.
• Ions may gain or lose electrons but retain the same nucleus.
• Nucleons = protons + neutrons.

Concept / Approach:

By definition, atomic number Z is the count of protons in the nucleus. While a neutral atom also has Z electrons, electron count can change during ionization without altering elemental identity. Neutron count can vary, producing isotopes (same Z, different mass number A). Thus, Z strictly equals the number of protons.

Step-by-Step Solution:

Verification / Alternative check:

Periodic table ordering by increasing Z confirms definition; isotopes share Z but have different neutron counts.

Why Other Options Are Wrong:

neutrons: Determine isotopes, not elemental identity. electrons: Vary in ions. either electrons or protons: Misleading; only protons define Z. nucleons: Total of protons plus neutrons defines mass number A, not Z.

Common Pitfalls:

Equating neutrality with identity; forgetting that ions are still the same element.

Final Answer:

protons