Oxygen

Oxygen
8O
- ↑ O ↓ S Periodic table Nitrogen ← oxygen → Fluorine
Appearance
colorless gas; pale blue liquid. Oxygen bubbles rise in this photo of liquid oxygen.
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General properties
Name, symbol, number	oxygen, O, 8
Pronunciation	/ˈɒksɨdʒən/ OK-si-jən
Element category	nonmetals
Group, period, block	N/A, 2, p
Standard atomic weight	15.999
Electron configuration	[He] 2s22p4 2, 6 File:Electron shell 008 Oxygen (nonmetal) - no label.svg
History
Discovery	Carl Wilhelm Scheele
Physical properties
Phase	gas
Density (near r.t.	(0 °C, 101.325 kPa) 1.429 g/L
Liquid density at m.p.	1.141 g·cm-3
Melting point	54.36 K
Boiling point	90.20 K
Critical point	154.59 K
Heat of fusion	(O2) 0.444 kJ·mol-1
Atomic properties
Oxidation states	2, 1, -1, -2
Electronegativity	3.44 (Pauling scale)
Covalent radius	66±2 pm
Van der Waals radius	152 pm
Crystal structure	cubic
Speed of sound (thin rod)	(gas, 27 °C) 330 m·s-1
CAS registry number	7782-44-7
Most stable isotopes
Main article: Isotopes of oxygen
iso NA half-life DM DE (MeV) DP 16O nat
v • t • e • r

Oxygen is chemical element with symbol O and atomic number is 8 Its name derives from the Greek roots ὀξύς (oxys) ("acid", literally "sharp", referring to the sour taste of acids) and -γόνος (-gοnos) ("producer", literally "begetter"), because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition. At standard temperature and pressure, two atoms of the element bind to form a colorless, odorless, tasteless diatomic gas with the formula O2. This substance is an important part of the atmosphere.

Oxygen is a member of the chalcogen group on the periodic table and is a highly reactive nonmetallic element that readily forms compounds with most elements except the noble gases Helium and Neon. Oxygen is a strong oxidizing agent and only fluorine has greater electronegativity. Oxygen is too chemically reactive to remain a free element in Earth's atmosphere without being continuously replenished by the photosynthetic action of living organisms, which use the energy of sunlight to produce elemental oxygen from water. Free elemental O₂ only began to accumulate in the atmosphere about 2.5 billion years ago (see Great oxygenation event) about a billion years after the first appearance of these organisms. Diatomic oxygen gas constitutes 20.8% of the volume of air.

Oxygen constitutes most of the mass of living organisms, because water is their major constituent (for example, about two-thirds of human body mass[6]). Many major classes of organic molecules in living organisms, such as proteins, nucleic acids, carbohydrates, and fats, contain oxygen, as do the major inorganic compounds that are constituents of animal shells, teeth, and bone. Elemental oxygen is produced by cyanobacteria, algae and plants, and is used in cellular respiration for all complex life. Oxygen is toxic to obligately anaerobic organisms, which were the dominant form of early life on Earth until O₂ began to accumulate in the atmosphere. Another form (allotrope) of oxygen, ozone (O₃), strongly absorbs UVB radiation and consequently the high-altitude ozone layer helps protect the biosphere from ultraviolet radiation, but is a pollutant near the surface where it is a by-product of smog. At even higher low earth orbit altitudes, atomic oxygen is a significant presence and a cause of erosion for spacecraft.

By particle count (molar) or mass basis, oxygen is the third most abundant element in the universe. It is also by far the most abundant element in earth's crust on either basis

Oxygen was discovered independently by Carl Wilhelm Scheele, in Uppsala, in 1773 or earlier, and Joseph Priestley in Wiltshire, in 1774, but Priestley is often given priority because his work was published first. The name oxygen was coined in 1777 by Antoine Lavoisier, whose experiments with oxygen helped to discredit the then-popular phlogiston theory of combustion and corrosion. Oxygen is produced industrially by fractional distillation of liquefied air, use of zeolites with pressure-cycling to concentrate oxygen from air, electrolysis of water and other means. Uses of elemental oxygen include the production of steel, plastics and textiles, brazing, welding and cutting of steels and other metals, rocket propellant, oxygen therapy and life support systems in aircraft, submarines, spaceflight and diving.

The critical point of oxygen occurs at T = 154.6 K and p = 5050 bar (49.8 atm). The element cannot be liquified by compression alone, but must be cooled as well. Oxygen can be solidified by high pressure alone. There are six known solid phases. Of these, three - the alpha, beta, and gamma phases - form at low temperature and pressure. The others - delta, epsilon, and zeta phases - can form at ambient and even high temperature, but only at pressures above 90000 atm. Interestingly, while liquid oxygen and the three low-pressure forms of solid oxygen are blue, the delta oxygen phase is orange and the epsilon phase is dark red to black. Color of the zeta phase is unknown, but the substance itself is metallic.

Oxygen Compound

Some oxygen compounds:

• Water
• Calcium oxide
• Oxygen fluoride
• Beryllium oxide
• Hydronium ion
• Magnesium oxide
• Strontium oxide
• Sodium hydroxide
• Potassium hydroxide

and other.

References

9-Period Periodic Table of Elements
1	1 H																																																																	2 He
2	3 Li	4 Be																																																																	5 B	6 C	7 N	8 O	9 F	10 Ne
3	11 Na	12 Mg																																																																	13 Al	14 Si	15 P	16 S	17 Cl	18 Ar
4	19 K	20 Ca																																																																	21 Sc	22 Ti	23 V	24 Cr	25 Mn	26 Fe	27 Co	28 Ni	29 Cu	30 Zn	31 Ga	32 Ge	33 As	34 Se	35 Br	36 Kr
5	37 Rb	38 Sr																																																																	39 Y	40 Zr	41 Nb	42 Mo	43 Tc	44 Ru	45 Rh	46 Pd	47 Ag	48 Cd	49 In	50 Sn	51 Sb	52 Te	53 I	54 Xe
6	55 Cs	56 Ba																																																					57 La	58 Ce	59 Pr	60 Nd	61 Pm	62 Sm	63 Eu	64 Gd	65 Tb	66 Dy	67 Ho	68 Er	69 Tm	70 Yb	71 Lu	72 Hf	73 Ta	74 W	75 Re	76 Os	77 Ir	78 Pt	79 Au	80 Hg	81 Tl	82 Pb	83 Bi	84 Po	85 At	86 Rn
7	87 Fr	88 Ra																																																					89 Ac	90 Th	91 Pa	92 U	93 Np	94 Pu	95 Am	96 Cm	97 Bk	98 Cf	99 Es	100 Fm	101 Md	102 No	103 Lr	104 Rf	105 Db	106 Sg	107 Bh	108 Hs	109 Mt	110 Ds	111 Rg	112 Cn	113 Nh	114 Fl	115 Mc	116 Lv	117 Ts	118 Og
8	119 Uue	120 Ubn																															121 Ubu	122 Ubb	123 Ubt	124 Ubq	125 Ubp	126 Ubh	127 Ubs	128 Ubo	129 Ube	130 Utn	131 Utu	132 Utb	133 Utt	134 Utq	135 Utp	136 Uth	137 Uts	138 Uto	139 Ute	140 Uqn	141 Uqu	142 Uqb	143 Uqt	144 Uqq	145 Uqp	146 Uqh	147 Uqs	148 Uqo	149 Uqe	150 Upn	151 Upu	152 Upb	153 Upt	154 Upq	155 Upp	156 Uph	157 Ups	158 Upo	159 Upe	160 Uhn	161 Uhu	162 Uhb	163 Uht	164 Uhq	165 Uhp	166 Uhh	167 Uhs	168 Uho	169 Uhe	170 Usn	171 Usu	172 Usb
9	173 Ust	174 Usq
Alkali metal Alkaline earth metal Lanthanide Actinide Superactinide Transition metal Post-transition metal Metalloid Other nonmetal Halogen Noble gas predicted predicted predicted predicted predicted predicted predicted predicted predicted