The letters J and Q are not found on the periodic table.

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The letters “J” and “Q” are the only two letters not found on the periodic table. These letters do not occur in either element symbols or element names. However, you could find both letters on the periodic table in the past and may find them still on certain charts.

The Letter J on the Periodic Table

The letter J was the element symbol for iodine in Mendeleev’s 1871 periodic table.

You won’t find the letter “J” on the IUPAC periodic table of the elements. However, J was the symbol for the element jod or iodine on Mendeleev’s periodic table. In some countries (e.g., Norway, Poland, Sweden, Serbia, Croatia), the element iodine is known by the name jod, even though the international element symbol is I. The German word for iodine is Iod or Jod (nouns are always capitalized in German). The Jod-Basedow effect gets its name from the element Jod and the name of the physician who first described the syndrome. The Jod-Basedow effect is hypothyroidism resulting from administration of iodide or iodine.

Many people thought the discovery of element 113 by the Japanese RIKEN team would lead to an element name beginning with the letter J. But, the researchers went with the name nihonium with symbol Nh, honoring the Japanese name for their country, Nihon koku.

The Letter Q on the Periodic Table

The letter “Q” does not occur in any official element name. However, it was the temporary or placeholder name for element 114. After its official discovery, element 114 was named flerovium. Its placeholder name was ununquadrium, which means “one one four.” The extended periodic table, which includes undiscovered elements, still includes the letter Q. The placeholder name for element 124 is unbiquadium, with element symbol Ubq.

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IUPAC Rules for Temporary Names

IUPAC temporary names describe undiscovered elements by their atomic number. The only way an element will get a “J” in its name is if a discoverer chooses the letter, but the letter “Q” occurs in any temporary name containing the number four:

IUPAC temporary name rules


Mendeleev, Dmitrii. (1871). Zhurnal Russkoe Fiziko-Khimicheskoe Obshchestvo 3, 25; German version: “Die periodische Gesetzmässigkeit der chemischen Elemente.” Annalen der Chemie und Pharmacie. Supplement 8, 133-229.Mendeleev, Dmitrii (1889). “The Periodic Law of the Chemical Elements.” Journal of the Chemical Society (London) 55, 634-656.


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