Commission on the Nomenclature of Inorganic Chemistry

Recommendations for the Naming of Elements of Atomic Numbers Greater than 100

(Rules Approved 1978)

World Wide Web version Prepared by G. P. Moss

School of Biological and Chemical Sciences, Queen Mary and Westfield College,
Mile End Road, London, E1 4NS, UK

These Rules are as close as possible to the published version prepared by J. Chatt [see Pure Appl. Chem., 1979, 51, 381-384. Copyright IUPAC, reproduced with the permission of IUPAC]. If you need to cite these rules please quote these references as their source.

A PDF of the document is available.

Recommendations for the Naming of Elements of Atomic Numbers Greater than 100

Elements of atomic numbers of 101 to 103 have trivial names and corresponding two letter symbols approved by IUPAC. The status of these names and symbols is in no way affected by the recommendation of systematic names for elements of atomic numbers greater than 100.

Elements of atomic numbers greater than 103 are often referred to in the scientific literature but receive names only after they have been 'discovered'. Names are needed for indexing and other purposes and the Commission on Nomenclature of Inorganic Chemistry was asked to make recommendations concerning names and symbols of the heavy 'unknown' elements. The Commission decided that these elements would be best named systematically and that names should accord with the following principles:

(i) The names should be short and obviously related to the atomic numbers of the elements.

(ii) The names should end in 'ium' whether the element was expected to be a metal or otherwise.

(iii) The symbols for the systematically named elements should consist of three letters.

(iv) The symbols should be derived directly from the atomic numbers and be visually related to the names as far as possible.

The reasons for principles (i), (ii), and (iv) are obvious but those for (iii) are not so immediately apparent. The Commission recommends the use of three-letter symbols because any systematically derived set of two-letter symbols will tend to duplicate some of the two-letter symbols of elements of atomic numbers less than 104. Any ad hoc method of removing such duplication will destroy the systematic derivation of the symbol.

The existence of a systematic nomenclature for the unknown elements does not deny the right of 'discoverers' of new elements to suggest other names to the Commission after their discovery has been established beyond all doubt in the general scientific community. For elements 101-103 the systematic names are minor alternatives to the trivial names already approved by IUPAC. The systematic names and symbols for elements of atomic numbers greater than 103 are the only approved names and symbols for those elements until the approval of trivial names by IUPAC.

Nomenclature of Elements of Atomic Numbers greater than 100

1. The name is derived directly from the atomic number of the element using the following numerical roots:

0 = nil3 = tri6 = hex9 = enn
1 = un4 = quad7 = sept
2 = bi5 = pent8 = oct
2. The roots are put together in the order of the digits which make up the atomic number and terminated by 'ium' to spell out the name. The final 'n' of 'enn' is elided when it occurs before 'nil', and the final 'i' of 'bi' and of 'tri' when it occurs before 'ium'.

3. The symbol of the element is composed of the initial letters of the numerical roots which make up the name.

4. The root 'un' is pronounced with a long 'u', to rhyme with 'moon'. In the element names each root is to be pronounced separately.

101 Mendelevium (Unnilunium)Md*
102 Nobelium (Unnilbium)No*
103 Lawrencium (Unniltrium)Lr*
104 Unnilquadium Unq
105 Unnilpentium Unp
106 Unnilhexium Unh
107 Unnilseptium Uns
108 UnniloctiumUno
109 Unnilennium Une
110 Ununnilium Uun
111 UnununiumUuu
112 Ununbium Uub
113 Ununtrium Uut
114 Ununquadium Uuq
115 Ununpentium Uup
116 Ununhexium Uuh
117 Ununseptium Uus
118 Ununoctium Uuo
119 Ununennium Uue
120 Unbinilium Ubn
121 UnbiuniumUbu
130 Untrinilium Utn
140 Unquadnilium Uqn
150 Unpentnilium Upn
160 Unhexnilium Uhn
170 Unseptnilium Usn
180 Unoctnilium Uon
190 Unennilium Uen
200 Binilnilium Bnn
201 Binilunium Bnu
202 Binilbium Bnb
300 Trinilnilium Tnn
400 Quadnilnilium Qnn
500 Pentnilnilium Pnn
900 Ennilnilium Enn
* To correspond to the systematic names, the systematic symbols would be Unu, Unb and Unt respectively.

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