Allotropes of oxygen

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(Redirected from
Molecular oxygen
)

There are several known allotropes of oxygen. The most familiar is molecular oxygen (O2), present at significant levels in Earth's atmosphere and also known as dioxygen or triplet oxygen. Another is the highly reactive ozone (O3). Others are:

  • Atomic oxygen (O1), a free radical.
  • metastable states
    of molecular oxygen.
  • Tetraoxygen (O4), another metastable form.
  • Solid oxygen, existing in six variously colored phases, of which one is octaoxygen (O8, red oxygen) and another one metallic (ζ-oxygen).

Atomic oxygen

Atomic oxygen, denoted O or O1, is very reactive, as the individual atoms of oxygen tend to quickly bond with nearby molecules. Its lowest-energy electronic state is a

ultraviolet radiation results in a low Earth orbit atmosphere in which 96% of the oxygen occurs in atomic form.[1]

Atomic oxygen has been detected on Mars by Mariner, Viking, and the SOFIA observatory.[2]

Dioxygen

Further information: Oxygen
See also: Dioxygen in biological reactions
three-electron bonding
, shown here using dashed lines.

The common allotrope of elemental oxygen on Earth, O2, is generally known as oxygen, but may be called dioxygen, diatomic oxygen, molecular oxygen, dioxidene or oxygen gas to distinguish it from the element itself and from the triatomic allotrope

metastable. The doublet state requires an odd number of electrons, and so cannot occur in dioxygen without gaining or losing electrons, such as in the superoxide ion (O−2) or the dioxygenyl
ion (O+2).

The ground state of O2 has a bond length of 121 pm and a bond energy of 498 kJ/mol.[3] It is a colourless gas with a boiling point of −183 °C (90 K; −297 °F).[4] It can be condensed from air by cooling with liquid nitrogen, which has a boiling point of −196 °C (77 K; −321 °F). Liquid oxygen is pale blue in colour, and is quite markedly paramagnetic due to the unpaired electrons; liquid oxygen contained in a flask suspended by a string is attracted to a magnet.

Singlet oxygen

Main article: Singlet oxygen

porphyrins, or by chemical processes such as spontaneous decomposition of hydrogen trioxide in water or the reaction of hydrogen peroxide with hypochlorite
.

Ozone

Main article: Ozone

Triatomic oxygen (ozone, O3) is a very reactive allotrope of oxygen that is a pale blue gas at

laser printers, and photocopiers, as it is formed whenever air is subjected to an electrical discharge. It was named "ozon" in 1840 by Christian Friedrich Schönbein,[8] from ancient Greek ὄζειν (ozein: "to smell") plus the suffix -on, commonly used at the time to designate a derived compound and anglicized as -one.[9]

Ozone is

Ground-level ozone is an air pollutant that is especially harmful for senior citizens, children, and people with heart and lung conditions such as emphysema, bronchitis, and asthma.[11] The immune system produces ozone as an antimicrobial (see below).[12]

Cyclic ozone

Main article: Cyclic ozone

Cyclic ozone is a theoretically predicted O3 molecule in which its three atoms of oxygen bond in an equilateral triangle instead of an open angle.

Tetraoxygen

Main article: Tetraoxygen

Tetraoxygen had been suspected to exist since the early 1900s, when it was known as oxozone. It was identified in 2001 by a team led by Fulvio Cacace at the University of Rome.[13] The molecule O4 was thought to be in one of the phases of solid oxygen later identified as O8. Cacace's team suggested that O4 probably consists of two dumbbell-like O2 molecules loosely held together by induced dipole dispersion forces.

Phases of solid oxygen

Main articles: Solid oxygen and Octaoxygen

There are six known distinct phases of solid oxygen. One of them is a dark-red O8 cluster. When oxygen is subjected to a pressure of 96 GPa, it becomes

superconducting
.

References

  1. ^ "Out of Thin Air" Archived 2017-06-23 at the Wayback Machine.NASA.gov. February 17, 2011.
  2. ^ Bell, Kassandra (6 May 2016). "Flying observatory detects atomic oxygen in Martian Atmosphere". NASA. Archived from the original on 8 November 2020. Retrieved 30 September 2021.
  3. ^ Chieh, Chung. "Bond Lengths and Energies". University of Waterloo. Archived from the original on 14 December 2007. Retrieved 16 December 2007.
  4. ^ a b Chemistry Tutorial : Allotropes Archived 2021-11-17 at the Wayback Machine from AUS-e-TUTE.com.au
  5. ^ a b c Mellor 1939
  6. ISBN 0-471-17560-9
    .
  7. ^ Stwertka 1998, p.48
  8. ^ Christian Friedrich Schönbein, Über die Erzeugung des Ozons auf chemischen Wege Archived 2020-06-30 at the Wayback Machine, p. 3, Basel: Schweighauser'sche Buchhandlung, 1844.
  9. ^ "Ozone", Oxford English Dictionary online, retrieved 29 June 2020.
  10. ^ Stwertka 1998, p.49
  11. ^ "Who is most at risk from ozone?". airnow.gov. Archived from the original on 17 January 2008. Retrieved 2008-01-06.
  12. S2CID 36537588
    .
  13. PMID 12404493
    .
  14. PMID 12465476
    .

Further reading
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