The periodic table is the fundamental organizational chart in chemistry, visually arranging the 118 known chemical elements by their atomic number and recurring chemical properties. This structure, featuring rows called periods and columns called groups, is instantly recognizable. Given its importance, many people are confused about whether the name “periodic table” requires capitalization in general writing. This article clarifies the standard grammatical practice for this widely used term.
The General Rule for Capitalization
The definitive rule in most standard prose and scientific publications is to write the term in lowercase letters. The correct form is “periodic table” unless it begins a sentence. This practice is consistent across major editorial guidelines, including those used in academic and journalistic settings. When writing about the subject, treat it as a descriptive noun phrase rather than a unique, formally named entity. For instance, a chemist might state that they frequently refer to the periodic table in their research.
Applying Common Versus Proper Noun Rules
The reason “periodic table” is generally lowercase is rooted in its grammatical classification as a common noun. A common noun refers to a general category of things, like “ocean” or “mountain,” while a proper noun refers to a specific, unique person, place, or thing, which is always capitalized, such as “Mount Everest” or “Pacific Ocean.” The term “periodic table” describes a type of chart that follows a specific organizational principle—the periodic law—not a unique, one-of-a-kind artifact. Concepts like “solar system” or “food pyramid” are treated similarly, remaining in lowercase because they describe a general system or model. The individual names of the scientists who contributed to its development, such as the Russian chemist Dmitri Mendeleev, are proper nouns and remain capitalized.
Specific Instances Requiring Capitalization
There are limited situations where capitalization of the phrase “periodic table” is appropriate, primarily when it functions as a title or a formal, specific name. When the term is used as part of a formal heading or the official title of a document, it must follow title capitalization rules. For example, a reference might be cited as The Modern Periodic Table of the Elements. Capitalization is also correct when the phrase is used to name a specific, labeled figure or chart within a text, such as “See Figure 1: The Periodic Table of Elements.” Furthermore, a historical designation that uses the phrase as a proper name, like “Mendeleev’s Periodic Table of Elements,” requires capitalization to distinguish that specific, historical iteration of the chart.