94 elements occur naturally on earth. These are shown in 
red when only natural radioactive isotopes are known. The elements highlighted
in yellow are those that do not exist naturally on our planet but have been created
artificially, usually by bombarding heavy atom targets with ions. Curium was the first
artificial element to be made, in 1944, as a result of helium ion bombardment of
plutonium-239. The creation of an atom of |unnilennium| was reported ten
years ago and now element 110 has been made, currently the last element in the periodic
table. But the atoms of these esoteric elements have extremely short lives, the matter of
a few milliseconds. For this reason it has proved difficult to validate their existence and
study their chemistry.
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Particularly for the transactinide elements, which run from atomic number 104,
there was some dispute over their discovery. Russian scientists first reported element-104
in 1964 and named it kurchatovium, but American scientists doubted the assignment and
claimed its discovery in 1969, calling it rutherfordium. So who should name it? The
International Unions of Pure and Applied Chemistry and Physics adopted a temporary
compromise. They named element-104 unnilquadium, which spells out one-0-four with
un for one, nil for zero and quad for four, and the usual ium ending to indicate a
metallic element. The temporary names of the succeeding elements follow in the same
way. So the final element in our table is un-un-nilium (Uun).