periodic law
Definition
Noun: - A fundamental principle in chemistry: The Periodic Law states that the physical and chemical properties of the elements are periodic functions of their atomic numbers. This means that when elements are arranged in order of increasing atomic number, elements with similar properties recur at regular intervals.
Usage
The term "periodic law" is used to describe the scientific rule that governs the organization of the periodic table of elements. - It is a foundational concept in chemistry. - It explains the pattern and predictability of elemental properties.
Examples
- The development of the modern periodic table is based directly on the periodic law.
- Mendeleev's early table predicted unknown elements, but the modern form, organized by atomic number, perfectly illustrates the periodic law.
- Understanding the periodic law allows chemists to predict the behavior of elements.
Advanced Usage
- In scientific discourse: The periodic law is often discussed in the context of its historical development, contrasting Mendeleev's version (based on atomic mass) with the modern version (based on atomic number).
- As a governing principle: It is cited to explain trends in the periodic table, such as atomic radius, ionization energy, and electronegativity.
Variants and Related Words
- Periodicity (noun): The quality or character of being periodic; the recurrence of similar properties at regular intervals, as embodied by the periodic law.
- Periodic Table (noun): The tabular arrangement of the chemical elements, organized on the basis of the periodic law.
Synonyms
- Mendeleev's Law: Often used historically to refer to the initial formulation of the periodic law by Dmitri Mendeleev, though it was based on atomic weight.
Related Phrases and Concepts
- Periodic Trend: A specific pattern in elemental properties (e.g., electronegativity increasing across a period) that is a direct consequence of the periodic law.
- Group (or Family): A vertical column on the periodic table containing elements with similar chemical properties, demonstrating the periodic law.
Noun
-
(chemistry) the principle that chemical properties of the elements are periodic functions of their atomic numbers
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