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Krypton

Chemical element, symbol Kr and atomic number 36 / From Wikipedia, the free encyclopedia

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Krypton (from Ancient Greek: κρυπτός, romanized: kryptos 'the hidden one') is a chemical element; it has symbol Kr and atomic number 36. It is a colorless, odorless, tasteless noble gas that occurs in trace amounts in the atmosphere and is often used with other rare gases in fluorescent lamps. Krypton is chemically inert.

Quick facts: Krypton, Pronunciation, Appearance, Standard ...
Krypton, 36Kr
Krypton_discharge_tube.jpg
A krypton-filled discharge tube glowing white
Krypton
Pronunciation/ˈkrɪptɒn/ (KRIP-ton)
Appearancecolorless gas, exhibiting a whitish glow in an electric field
Standard atomic weight Ar°(Kr)
Krypton in the periodic table
Ar

Kr

Xe
brominekryptonrubidium
Atomic number (Z)36
Groupgroup 18 (noble gases)
Periodperiod 4
Block  p-block
Electron configuration[Ar] 3d10 4s2 4p6
Electrons per shell2, 8, 18, 8
Physical properties
Phase at STPgas
Melting point115.78 K (−157.37 °C, −251.27 °F)
Boiling point119.93 K (−153.415 °C, −244.147 °F)
Density (at STP)3.749 g/L
when liquid (at b.p.)2.413 g/cm3[3]
Triple point115.775 K, 73.53 kPa[4][5]
Critical point209.48 K, 5.525 MPa[5]
Heat of fusion1.64 kJ/mol
Heat of vaporization9.08 kJ/mol
Molar heat capacity20.95[6] J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 59 65 74 84 99 120
Atomic properties
Oxidation states0, +1, +2 (rarely more than 0; oxide is unknown)
ElectronegativityPauling scale: 3.00
Ionization energies
  • 1st: 1350.8 kJ/mol
  • 2nd: 2350.4 kJ/mol
  • 3rd: 3565 kJ/mol
Covalent radius116±4 pm
Van der Waals radius202 pm
Color lines in a spectral range
Spectral lines of krypton
Other properties
Natural occurrenceprimordial
Crystal structure face-centered cubic (fcc) (cF4)
Lattice constant
Face-centered cubic crystal structure for krypton
a = 583.57 pm (at triple point: 115.78 K)[7]
Thermal conductivity9.43×10−3  W/(m⋅K)
Magnetic orderingdiamagnetic[8]
Molar magnetic susceptibility−28.8×10−6 cm3/mol (298 K)[9]
Speed of sound(gas, 20 °C) 221 m·s−1
(liquid) 1120 m/s
CAS Number7439-90-9
History
Discovery and first isolationWilliam Ramsay and Morris Travers (1898)
Isotopes of krypton
Main isotopes[10] Decay
abun­dance half-life (t1/2) mode pro­duct
78Kr 0.360% 9.2×1021 y[11] εε 78Se
79Kr synth 35 h ε 79Br
β+ 79Br
γ
80Kr 2.29% stable
81Kr trace 2.3×105 y ε 81Br
81mKr synth 13.10 s IT 81Kr
ε 81Br
82Kr 11.6% stable
83Kr 11.5% stable
84Kr 57.0% stable
85Kr trace 11 y β 85Rb
86Kr 17.3% stable
Symbol_category_class.svg Category: Krypton
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Krypton, like the other noble gases, is used in lighting and photography. Krypton light has many spectral lines, and krypton plasma is useful in bright, high-powered gas lasers (krypton ion and excimer lasers), each of which resonates and amplifies a single spectral line. Krypton fluoride also makes a useful laser medium. From 1960 to 1983, the official definition of meter was based on the wavelength of one spectral line of krypton-86, because of the high power and relative ease of operation of krypton discharge tubes.

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