化學元素是不是只有109種?

The element with atomic number larger than Uranium (92) are artificial elements (man made), many experiments are performed to make heavier elements, those artificial elements with larger atomic number are very unstable, they will dacay immediately. The most heaviest element should be 116 (or 118). You can search about Periodic Table to see more details.

2007-05-23 14:49:30 補充：
There is also isotope (同位素). Isotope of an element have the same atomic number (number of protons) as the original one, but different mass (number of neutrons). Deuterium (mass 2u) and Tritium (mass 3u) are isotopes of Hydrogen (mass 1u, atomic number 1). u is the atomic mass.

現在有118種

http://zh.wikipedia.org/wiki/%E5%85%83%E7%B4%A0%E5%91%A8%E6%9C%9F%E8%A1%A8

110
Ds
鐽 111
Rg
錀 112
Uub
113
Uut
114
Uuq
115
Uup
116
Uuh
117
Uus
118
Uuo