Periodic Law

Properties of elements are periodic functions of atomic number.

Short definition

Properties of elements are periodic functions of atomic number.

Full explanation

Periodic Law in the context of periodic table trends: Properties of elements are periodic functions of atomic number. In practice this means relating macroscopic observation (mass, pressure, color), particle-level picture (atoms, electrons, ions moving and rearranging), and symbolic representation (formulas, equations, units). For Periodic Law, students connect the definition to linked lessons: do not just memorize the phrase — predict what changes when conditions change and check with dimensional analysis.

Notation and units

• Notation: —
• Common units: SI or derived, temperature in kelvins when in gas/energy contexts.
• Symbolic hint: See related formula if applicable.

Example

Example for periodic law: In a worked problem where this term appears, substitute measured values with correct units and check that the dimensional result matches the intended quantity. For instance, calculating a periodic law often uses the form $n=m/M$ or $c=n/V$ or $PV=nRT$ with $T$ in kelvins — illustrating how periodic law leads to a numerically different but dimensionally correct result when units are handled.

Confused with

• Periodic Trend — distinction: Periodic Law is properties of elements are periodic functions of atomic number. while Periodic Trend has a different defining property. See cross-link in glossary.

Related resources

• Topic: periodic-table-trends
• Formula library — when a specific equation involves this term it is linked.
• Constants — if a constant is required, it is sourced and versioned (NIST 2022).

Sources

• NIST Physical Constants 2022 (nist-2022, CODATA 2022). Accessed 2026-08-21.

Last reviewed: 2026-08-21 — Review due: 2027-08-21 — Author: Chemistry Fundamentals Editorial Team — Reviewer: Editorial Review Board (transparent placeholder).

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