IUPAC Nomenclature ($Z>100$)

When scientists synthesize elements with atomic number Z greater than 100, there is often a significant delay — sometimes years or even decades — before the international chemistry community agrees on an official name. During this waiting period, the International Union of Pure and Applied Chemistry (IUPAC) uses a systematic, language-neutral naming system so that chemists worldwide can communicate unambiguously about these superheavy elements. This system generates both a temporary name and a two-letter symbol directly from the element's atomic number using Latin and Greek numerical roots. The IUPAC systematic nomenclature for elements with Z > 100 was formalized in 1979 and updated in 1997 to ensure consistency. The scheme works by converting each digit of the atomic number into a designated root word, concatenating those roots in order, and appending the suffix '-ium'. The resulting symbol is formed by taking the first letter of each numerical root. For example, element 105 was temporarily called 'Unnilpentium' (symbol Unp) before receiving its permanent name Dubnium (Db). This system eliminates the confusion that arises when competing research groups from different countries propose different national names for the same element. Understanding this nomenclature is important not only for chemistry competitions and university entrance examinations, but also because it reveals how science manages priority disputes through systematic, culturally neutral conventions. The periodic table currently extends to element 118 (Oganesson), and all elements beyond approximately Z = 104 were named using the IUPAC temporary system before receiving permanent names. Future elements, likely to be synthesized in the 2020s and beyond, will again carry these systematic names until official naming occurs.

Key takeaways
  • Learn the Numerical Roots
  • Concatenate the Roots in Digit Order
  • Form the Chemical Symbol
  • Apply Phonetic Smoothing Rules
  • Permanent Names Replace Systematic Names

Learn the Numerical Roots

Each digit 0–9 corresponds to a Latin or Greek root: 0 = nil, 1 = un, 2 = bi, 3 = tri, 4 = quad, 5 = pent, 6 = hex, 7 = sept, 8 = oct, 9 = enn. These roots are language-neutral, derived from a mix of Latin (nil, un, bi, tri, quad) and Greek (pent, hex, sept, oct, enn) to avoid favouring any single modern language.

Concatenate the Roots in Digit Order

Write the atomic number digit by digit from left to right. Replace each digit with its root. For Z = 119: digits are 1, 1, 9 → roots are un + un + enn. Join them: 'ununenn'. Add the suffix '-ium' → 'Ununennium'. Small phonetic adjustments apply: when a root ending in a vowel precedes another root beginning with a vowel, one vowel is dropped to ease pronunciation (e.g., 'ennnil' becomes 'ennil', and 'bii' simplifies to 'bi').

Form the Chemical Symbol

Take the first letter of each numerical root (capitalise the first letter only) and combine them into a three-letter symbol. For Ununennium (119): U (un) + U (un) + e (enn) = Uue. For Unbinilium (120): U (un) + b (bi) + n (nil) = Ubn. The symbol always has exactly as many letters as the atomic number has digits — three letters for three-digit atomic numbers.

Apply Phonetic Smoothing Rules

IUPAC specifies two elision rules to prevent awkward double-vowels: (a) 'bi' before 'ium' stays 'bi' → suffix becomes '-ium' with no change; (b) 'enn' before 'nil' contracts to 'en-nil' (one 'n' dropped). Example: element 109 = un + nil + enn + ium → 'Unnilennium' — note the double 'n' in 'unnilennium' is kept because 'un' ends in 'n' and 'nil' begins with 'n', but these belong to different roots, so both are retained. The IUPAC official spelling is 'Unnilennium', symbol Une.

Permanent Names Replace Systematic Names

Once the discovery is officially verified and credited by IUPAC, the discovering research group proposes a permanent name (often honouring a scientist, institution, or place). IUPAC then approves it after a public comment period. For example: Unnilennium (Une, Z = 109) became Meitnerium (Mt), named after physicist Lise Meitner. Ununoctium (Uuo, Z = 118) became Oganesson (Og), honouring Yuri Oganessian. The systematic name is then retired from active use but remains in historical literature.

The Key Equation

Digit sequence: d1d2d3⟶root(d1)+root(d2)+root(d3)+ium\text{Digit sequence: } d_1 d_2 d_3 \longrightarrow \text{root}(d_1) + \text{root}(d_2) + \text{root}(d_3) + \text{ium}
  • d_1, d_2, d_3 — Digits of atomic number Z (dimensionless): Individual digits of the atomic number written from most significant to least significant. For Z = 115: d1 = 1, d2 = 1, d3 = 5.
  • \text{root}(d) — Numerical root (dimensionless): The Latin/Greek word fragment assigned to digit d: nil(0), un(1), bi(2), tri(3), quad(4), pent(5), hex(6), sept(7), oct(8), enn(9).
  • \text{ium} — Element suffix (dimensionless): Standard IUPAC suffix for metals, appended after all roots to denote it is a chemical element name.

Worked Example

Problem. Determine the IUPAC systematic name and symbol for the element with atomic number Z = 114, and state its permanent IUPAC name.

Z=114⇒un⏟1un⏟1quad⏟4ium=Ununquadium (Uuq)→IUPAC 2012Flerovium (Fl)Z = 114 \Rightarrow \underbrace{\text{un}}_{1}\underbrace{\text{un}}_{1}\underbrace{\text{quad}}_{4}\text{ium} = \text{Ununquadium (Uuq)} \xrightarrow{\text{IUPAC 2012}} \text{Flerovium (Fl)}

Answer. Systematic name: Ununquadium, Symbol: Uuq. Permanent name: Flerovium (Fl).

Figure
Diagram
IUPAC Systematic Naming: Digit Root Table & Example Z=109Digit → Root → Symbol LetterDigitRootLetter0niln1unu2bib3trit4quadq5pentp6hexh7septs8octo9enneWorked Example: Z = 1091 0 9Digit 1Digit 0Digit 9unnilennConcatenate + add -ium:UnnilenniumSymbol (1st letters):UnePermanent name:Meitnerium (Mt)
Origins · 1 minLise Meitner and how this was discovered
LM
Lise Meitner
1878–1968 · Austrian-Swedish

Lise Meitner was a pioneering nuclear physicist who co-discovered nuclear fission in 1938 alongside Otto Hahn and Fritz Strassmann, providing the theoretical explanation for why uranium nuclei split when bombarded with neutrons. Her application of Einstein's mass-energy equivalence (E = mc²) to calculate the enormous energy released during fission was crucial to understanding the process. Although she was controversially excluded from the 1944 Nobel Prize awarded to Hahn alone, her legacy is immortalised in the naming of element 109 — Meitnerium (Mt) — in her honour by IUPAC in 1997. She is the only non-mythological woman to have an element named solely after her. Albert Einstein reportedly called Lise Meitner 'our Marie Curie', and she received 48 nominations for the Nobel Prize without ever winning it — one of the greatest oversights in Nobel history.

  • Organisation of the Modern Periodic Table — Understanding how elements are arranged by atomic number Z provides the foundational context for why systematic naming of new elements by Z is necessary.
  • Transactinide and Superheavy Elements (Z > 103) — Superheavy elements beyond lawrencium are the primary targets of IUPAC systematic nomenclature and are synthesised through nuclear fusion reactions in particle accelerators.
  • Island of Stability in Nuclear Physics — Theoretical predictions of magic proton and neutron numbers that confer extra stability to superheavy nuclei explain why scientists continue to synthesise elements well beyond Z = 118.
  • Atomic Number and Nuclear Structure — The atomic number Z (number of protons) is the sole input to the IUPAC systematic naming scheme, making a clear understanding of Z essential for applying these naming rules correctly.