Dmitri Mendeleev

Dmitri Mendeleev was a Russian chemist who formulated the periodic law and published an influential periodic table in 1869, predicting properties of elements not yet discovered.

Periodic law: The principle that elemental properties recur periodically when elements are arranged by increasing atomic number. Mendeleev's original law organized elements by atomic weight and established the pattern behind his table.
Atomic weight: The weighted average mass of an element's atoms relative to a standard, usually expressed in atomic mass units. Mendeleev chiefly ordered elements by this quantity, while adjusting placements to preserve chemical patterns.
History of the periodic table: The development of systems for classifying chemical elements, culminating in the modern periodic table. Mendeleev's 1869 arrangement was a landmark in a longer search for elemental order.
Julius Lothar Meyer: A German chemist who independently developed a periodic classification of the elements in the 1860s. Meyer's parallel work makes clear that periodic classification was a shared scientific problem.
Julius Lothar Meyer's periodic table: A periodic classification of elements independently developed by Julius Lothar Meyer in the 1860s. Meyer displayed periodicity, but Mendeleev's published predictions gave his table greater influence.
Periodic table: A tabular arrangement of chemical elements that displays recurring patterns in their properties. Mendeleev's table became the model for the modern arrangement of the elements.
Chemical periodicity: The recurrence of chemical and physical properties among elements as their atomic numbers increase. Recurring properties supplied the pattern Mendeleev used to arrange elements and identify gaps.
St. Petersburg State University: A Russian public research university founded in 1724 and based in Saint Petersburg. Mendeleev studied and taught chemistry there, including while preparing his textbook.
John Newlands: An English chemist who proposed the law of octaves, arranging elements in repeating groups in 1865. His scheme anticipated periodic recurrence but lacked Mendeleev's successful predictions of undiscovered elements.
Law of octaves: John Newlands's proposal that similar elemental properties recur at intervals of eight when elements are ordered by atomic weight. Newlands's fixed pattern contrasts with Mendeleev's willingness to leave gaps and revise placements.

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