Group 18 / VII; Noble Gases

Noble gases do not react with other elements. Almost but not quite true - there are a few noble gas compounds like fluorides, see below.
Noble gases remain gases down to very low temperatures. Helium (He) turns liquid at 4.2 K (- 269 oC; -452 oF) and does not turn solid at normal pressure. It is absolutely indispensable for low temperature physics and applications.
The other noble gases are of some importance, too. Neon (Ne) gave the name to "neon tubes", i.e. florescent lights. Important uses are simply as absolutely inert protection gases, e.g. in argon (Ar) welding or inside furnaces and low-pressure equipment like plasma etchers. Compounds like Argon or Krypton (Kr) fluorides (ArF3, KrF3) are of prime importance for Lasers needed to make modern microelectronic chips.
Radon is radioactive and constantly produced in small quantities by the decay of naturally occurring uranium (U).
Table of Basic Data
 
Name
(German)		 Helium
Helium 		Neon
Neon 		Argon
Argon 		Krypton
Krypton 		Xenon
Xenon 		Radon
Radon
Atomic number 2 10 18 36 54 86
Atomic mass [u] 4,00 20,18 39,95 83,8 131,29 222,02
Melting point [K] - 24,48 83,78 61.6120,85 166,1 211,4
Melting point [oC] - -248,52 -189,22 -152,15 -106,9 -71
Melting point [oF] - -415 -308 -242 -161 -96
Boiling point [K] 4,216 27,1 87,29 120,85 166,1 211,4
Density [g/cm3] 0,17 0,84 1,66 3,48 4,49 9,23
Ionization energy [eV] 24,587 21,56 15,76 14,0 12,13 10,75
Electronegativitiy K.A. -- -- -- -- --
Atomic radius [pm] 128 K.A. 174 K.A. 218 K.A.
Ionic radius [pm] -- -- -- 169 190 K.A.
Oxidation numbers -- -- -- 2 2, 4, 6, 8 2
Lattice typ
Transformation temp. [oC] 		hcp fcc fcc fcc fcc fcc
Lattice constant [Å]
(a or c)		 ? ? ? ? ? ?
Young's - Modul us [GPa] ? ? ? ? ? ?
Therm. expansion coefficient a
[10-6K-1]		 ? ? ? ? ? ?
 
In case of doubt all numbers are for room temperatures
fcc = face centered cubic; lattice const. = a
bcc = body centered cubic
sc = simple cubic
hp = simple hexagonal
hcp = hexagonal close packed; lattice constants a and c.
op = simple orthorhombic, monoclinic, triclinic
tp = simple tetragonal
dia = diamond structure
r = trigonal or rhomboedral trigonal

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