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 .
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Krypton, 36 Kr A krypton-filled
discharge tube glowing white
Pronunciation (KRIP -ton ) Appearance colorless gas, exhibiting a whitish glow in an electric field
Atomic number (Z ) 36 Group group 18 (noble gases) Period period 4 Block p-block Electron configuration [ Ar ] 3d10 4s2 4p6 Electrons per shell 2, 8, 18, 8 Phase at STP gas Melting point 115.78 K (−157.37 °C, −251.27 °F) Boiling point 119.93 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 point 115.775 K, 73.53 kPa[4] [5] Critical point 209.48 K, 5.525 MPa[5] Heat of fusion 1.64 kJ/mol Heat of vaporization 9.08 kJ/mol Molar heat capacity 20.95[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
Oxidation states 0 , +1, +2 (rarely more than 0; oxide is unknown)Electronegativity Pauling scale: 3.00 Ionization energies 1st: 1350.8 kJ/mol 2nd: 2350.4 kJ/mol 3rd: 3565 kJ/mol Covalent radius 116±4 pm Van der Waals radius 202 pm Spectral lines of kryptonNatural occurrence primordial Crystal structure face-centered cubic (fcc) (cF4 )Lattice constant a = 583.57 pm (at triple point: 115.78 K)[7] Thermal conductivity 9.43×10−3 W/(m⋅K) Magnetic ordering diamagnetic [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 Number 7439-90-9 Discovery and first isolationWilliam Ramsay and Morris Travers (1898)
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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 .