Chemical element whole number. For example, the relative atomic mass of chlorine is 35.453 u, which differs greatly from a whole number as it is an average of about 76% chlorine-35 and 24% chlorine-37. Whenever a relative atomic mass value differs by more than 1% from a whole number, it is due to this averaging effect, as significant amounts of more than one isotope are naturally present in a sample of that element. Chemists and nuclear scientists have different definitions of a "pure element". In chemistry, a pure element means a substance whose atoms all (or in practice almost all) have the
Systematic element name for 4). There are two elision rules designed to prevent odd-looking names. The suffix "-ium" overrides traditional chemical suffix rules; thus elements 117 and 118 were "ununseptium" and "ununoctium", not "ununseptine" and "ununocton". This does not apply to the final trivial names these elements receive once confirmed; thus element 117 and 118 are now "tennessine" and "oganesson". For these trivial names, all elements receive the suffix "-ium", except those in group 17 which receive "-ine" (like the halogens) and those in group 18 which receive "-on" (like the noble gases). The systematic symbol is formed by taking the first letter