Definition check — what is an element? Choose the most accurate definition of an element from basic chemistry.

Introduction / Context:
In foundational chemistry, precise definitions help avoid misconceptions that cascade into errors about bonding, compounds, and mixtures. The term “element” is central to classifying matter.

Given Data / Assumptions:

• We are choosing among definitions, not examples.
• We assume standard IUPAC-style terminology for element, compound, and mixture.

Concept / Approach:
An element is a pure substance consisting of only one type of atom, characterized by a unique number of protons (atomic number). Elements can exist in various physical states and allotropic forms (e.g., O2, O3) but remain composed exclusively of atoms of that element. Compounds comprise two or more different elements bonded in definite proportions; mixtures combine substances physically without fixed ratios.

Step-by-Step Solution:
Identify the defining feature: atomic identity (same atomic number).Match to the option expressing “only one kind of atom.”Reject statements about charge, mixtures, or natural occurrence that do not define what an element is.

Verification / Alternative check:
Periodic table entries represent elements; samples like copper wire or sulfur crystals contain only Cu or S atoms, respectively, regardless of form.

Why Other Options Are Wrong:

• Always electrically charged: elements can be neutral or ionized; charge state does not define “element.”
• Mixture of compounds: describes mixtures, not elements.
• Found only in pure form in nature: many elements occur as minerals or combined states; purity is not required in nature.

Common Pitfalls:

• Confusing a chemical element with a pure sample; impurities do not change elemental identity.

Final Answer:
A substance made of only one kind of atom