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In chemistry, heavy transuranic elements receive a permanent trivial name and symbol only after their synthesis has been confirmed. This has been a protracted and highly political process in some cases (see element naming controversy). In order to discuss newly synthesized and as-yet unsynthesized elements without ambiguity, the IUPAC assigns a temporary systematic name and symbol to such elements. The origin of this idea came from the successful development of regular rules for the naming of organic compounds.

The IUPAC rules

digit	root	symbol
0	nil	n
1	un	u
2	b(i)	b
3	tr(i)	t
4	quad	q
5	pent	p
6	hex	h
7	sept	s
8	oct	o
9	en(n)	e

The temporary names are derived systematically from the element's atomic number. Each digit is translated to a 'numerical root', according to the table to the right. The roots are concatenated, and the name is completed with the ending -ium. Some of the roots are Latin and others are Greek; the reason is to avoid two digits starting with the same letter. There are two sandhi rules designed to prevent odd-looking names.

• If bi or tri is followed by the ending ium (i.e. the last digit is 2 or 3), the result is '-bium' or -'trium', not '-biium' or '-triium'.
• If enn is followed by nil (i.e. the sequence -90- occurs), the result is '-ennil-', not '-ennnil-'.

The systematic symbol is formed by taking the first letter of each root, converting the first to a capital.

The suffix -ium overrides traditional chemical suffix rules, thus 117 and 118 are ununseptium and ununoctium, not ununseptine and ununocton.

All elements up to and including atomic number 111 have received permanent trivial names and symbols, so the use of systematic names and symbols is recommended only for elements 112 and above. Therefore in practice, systematic names are just those with 3-letter symbols.

Element 119: Element 123: Element 208: Element 457: Element 986:

un + un + enn + ium =   un + bi + tr + ium =   bi + nil + oct + ium =   quad + pent + sept + ium =   enn + oct + hex + ium =

ununennium (Uue)   unbitrium (Ubt)   biniloctium (Bno)   quadpentseptium (Qps)   ennocthexium (Eoh)

Note: These examples show conjectured elements. As of 2006, ununoctium, element 118, is the highest element known.

• The IUPAC recommendation. Untitled draft, March 2004. (PDF, 143 kB).
• Systematic naming of Elements with Atomic Numbers Greater than 110 (PDF, 41 kB).