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Krypton (Kr)

QUICK REFERENCE

  • Symbol: Kr
  • Atomic Number: 36
  • Atomic Weight: 83.798
  • Element Classification: Noble Gas
  • Discovered By: Sir William Ramsay and Morris W. Travers
  • Discovery Date: 1898
  • Name Origin: Greek: ‘kryptos’ (hidden)
  • Density(g/cc): 0.003733 (at 0°C, 101.325 kPa)
  • Melting Point: -157.36°C
  • Boiling Point: -153.415°C
  • Appearance: Colorless, odorless, tasteless gas
  • Atomic Radius(pm): 88

Discovery

Krypton was discovered in 1898 by Sir William Ramsay and Morris W. Travers in London, England, during their research on the components of liquid air. After evaporating the components of liquid air, they found a residue of a previously unknown gas that showed brilliant green and orange spectral lines when excited. They named this new element krypton, from the Greek word ‘kryptos’, meaning hidden, to reflect its elusive nature.

Relation to Other Elements

Krypton is a member of the noble gases, which also include helium, neon, argon, xenon, and radon. These elements are located in group 18 of the periodic table and are characterized by their extremely low chemical reactivity due to their full valence electron shells. This makes them highly stable and not prone to forming chemical compounds under standard conditions. Among the noble gases, krypton is notable for its relatively higher density and its ability to form some compounds under specific conditions, although it remains largely inert.

Natural Occurrence

Krypton is a trace gas in the Earth’s atmosphere, making up about 1 part per million by volume. It is obtained commercially by fractional distillation of liquefied air, a process that also yields other noble gases. Krypton is rare and expensive compared to some of its noble gas counterparts due to its low concentration in the atmosphere.

Uses

Despite its scarcity and the challenges associated with its extraction, krypton has several important applications:

  • Lighting: Krypton is used in lighting applications, including fluorescent lamps and high-intensity, energy-efficient lighting, where it fills the space inside the bulb. Its use in lighting is due to its ability to produce a bright white light when electrified.
  • Photography and Projection: Krypton flash lamps are used in high-speed photography due to their intense and brief flashes of light.
  • Insulation: Krypton gas is used as an insulating material between the panes of double- and triple-glazed windows because of its low thermal conductivity.
  • Scientific Research: Krypton-86 was formerly used to define the standard meter, based on the orange-red spectral line of krypton. Although this definition has been superseded, krypton is still used in various scientific and metrological applications.

Krypton’s discovery marked an important milestone in the study of atmospheric gases and the understanding of noble gases’ chemical properties. Its specialized uses in lighting, insulation, and scientific research highlight the valuable applications of even the most inert elements.

Bromine (Br)

Rubidium (Rb)