Elemental Group 18
Group 1|
Group 2|
Group 3|
Group 4|
Group 5|
Group 6|
Group 7|
Group 8|
Group 9|
Group 10|
Group 11|
Group 12|
Group 13|
Group 14|
Group 15|
Group 16|
Group 17|
Group 18
| Noble Gases |
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The noble gases are the chemical elements in group 18 (old-style Group 0) of the periodic table. This chemical series contains helium, neon, argon, krypton, xenon, and radon.
Because of their unreactivity, the noble gases were not discovered until 1868, when helium was detected spectrographically in the Sun. The isolation of helium on Earth had to wait until 1895. The noble gases have very weak inter-atomic forces of attraction, and consequently very low melting points and boiling?points. This is why they are all gases under normal conditions, even those with larger atomic masses than many normally solid elements.
The periodic table contains an empty space under radon, with atomic number 118. This indicates the existence, albeit short-lived, of an as yet undiscovered noble gas, which has been temporarily named ununoctium.
Although noble gases are largely unreactive, they do form compounds under certain conditions. |
2
He
4.00260
|
10
Ne
20.18
|
18
Ar
39.95
|
36
Kr
83.80
|
54
Xe
131.3
|
86
Rn
(222.02)
|
118
Uuo
293.21
|
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