- Alternate uses: Krypton (planet), KRYPTON programming language
|
General |
Name, Symbol, Number | Krypton, Kr, 36 |
Chemical series | Noble gases |
Group, Period, Block | 18 (VIIIA), 4 , p |
Density, Hardness | 3.708 kg/m3 (273 K), NA |
Appearance | colorless |
Atomic Properties |
Atomic weight | 83.798 amu |
Atomic radius (calc.) | no data (88) pm |
Covalent radius | 110 pm |
van der Waals radius | 202 pm |
Electron configuration | [Ar]3d10 4s2 4p6 |
e- 's per energy level | 2, 8, 18, 8 |
Oxidation states (Oxide) | 0 (unknown) |
Crystal structure | Cubic face centered |
Physical Properties |
State of matter | gas (nonmagnetic) |
Melting point | 115.79 K (-251.25 °F) |
Boiling point | 119.93 K (-153.22 °F) |
Molar volume | 27.99 ×10-3 m3/mol |
Heat of vaporization | 9 .029 kJ/mol |
Heat of fusion | 1 .638 kJ/mol |
Vapor pressure | NA |
Speed of sound | 1120 m/s at 293.15 K |
Miscellaneous |
Electronegativity | 3.00 (Pauling scale) |
Specific heat capacity | 248 J/(kg*K) |
Electrical conductivity | no data |
Thermal conductivity | 0.00949 W/(m*K) |
1st ionization potential | 1350.8 kJ/mol |
2nd ionization potential | 2350.4 kJ/mol |
3rd ionization potential | 3565 kJ/mol |
4th ionization potential | 5070 kJ/mol |
5th ionization potential | 6240 kJ/mol |
6th ionization potential | 7570 kJ/mol |
7th ionization potential | 10710 kJ/mol |
8th ionization potential | 12138 kJ/mol |
Most Stable Isotopes |
iso | NA | half-life | DM | DE MeV | DP |
78Kr | 0.35% | Kr is stable with 42 neutrons |
80Kr | 2.25% | Kr is stable with 44 neutrons |
81Kr | {syn.} | 229000 y | Epsilon | 0.281 | 81Br |
82Kr | 11.6% | Kr is stable with 46 neutrons |
83Kr | 11.5% | Kr is stable with 47 neutrons |
84Kr | 57% | Kr is stable with 48 neutrons |
85Kr | {syn.} | 10.756 y | Beta- | 0.687 | 85Rb |
86Kr | 17.3% | Kr is stable with 50 neutrons |
|
SI units & STP are used except where noted. |
Krypton is a
chemical element in the
periodic table that has the symbol Kr and
atomic number 36. A colorless
noble gas, krypton occurs in trace amounts in the atmosphere, is isolated by fractionating liquefied air, and is often used with other rare gases in
fluorescent lamps. Krypton is
inert for most practical purposes but it is known to form compounds with
fluorine.
Krypton is a so-called noble gas due to its very low chemical reactivity and it is characterized by a brilliant
green and
orange spectral signature[?]. It is one of the products of
uranium fission. Solidified krypton is white and
crystalline with a face-centered cubic
crystal structure which is a common property of all "rare gases."
The international definition of the length of the
meter was, from 1960 to 1983, based on the light emitted by excited krypton atoms as a standard: specifically, the meter was defined as 1,650,763.73 wavelengths of the orange-red
emission line emitted by krypton-86 atoms.
Krypton clathrates[?] have been made with hydroquinone and phenol. Kr-85 is used in chemical analysis. When it is placed in various solids kryptonates[?] are formed and their activity is sensitive to surface chemical reactions. This noble gas is also used in photographic flash lamps needed for high-speed photography but this use is limited because of the high cost of krypton.
Krypton (
Greek kryptos meaning "hidden") was discovered in
1898 by
William Ramsay and
Morris Travers[?] in residue from evaporating nearly components of liquid air. In 1960 an international agreement defined the meter in terms of light emitted from a krypton isotope. This agreement replaced the longstanding
standard meter[?] located in
Paris which was a metal bar made of a
platinum-
iridium alloy (the bar was originally estimated to be one ten millionth of a quadrant of the
earth's polar circumference). In
October 1983 the krypton standard was in turn replaced by the
International Bureau of Weights and Measures. A meter is now defined as the distance that light traveles in a
vacuum during 1/299,792,458
s.
The concentration of this gas in earth's
atmosphere is about 1
ppm. It can be extracted from liquid air by
fractional distillation.
Like the other rare gases krypton is widely considered to be chemically inert. However, studies conducted since the
1960s have uncovered some
compounds of krypton. Krypton di
fluoride has been made in
gram quantities and can be produced in several different ways. Other fluorides and a
salt of a krypton called
oxyacid have also been found.
ArKr+ and Kr
H+
molecule-
ions have been investigated and there is evidence for Kr
Xe or KrXe+.
Naturally occurring krypton is composed of six
stable isotopes. Krypton's spectral signature is easily produced with some very sharp lines. Kr-81 is the product of atmospheric reactions with the other naturally occurring
isotopes of krypton. It is
radioactive with a
half-life of 250,000 years. Like
xenon, krypton is highly volatile when it is near surface waters and Kr-81 has therefore been used for dating old (50,000 - 800,000 year)
groundwater[?].
Kr-85 is an inert radioactive noble gas with a half-life of 10.76 years, that is produced by
fission of
uranium and
plutonium. Sources have included
nuclear bomb testing,
nuclear reactors, and the release of Kr-85 during the reprocessing of
fuel rods[?] from nuclear reactors. A strong gradient exists between the northern and southern hemispheres where concentrations at the
North Pole are approximately 30% higher than the
South Pole due to convective mixing.
Other uses: Krypton (planet),
KRYPTON programming language