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解説
元素記号 Ne ，原子番号 10，原子量 20.1797。周期表 18族，希ガス元素の1つ。ネオンは，大気中に 0.00182%含まれ，液体空気の分留によって得られる。1898年イギリスのW・ラムゼーらが液体空気の分留の過程でクリプトンに続いて発見し、新しい気体元素の意から、ギリシア語で「新しい」を意味するネオンneonに由来して命名した。乾燥大気中には容量で約1.8ppm含まれている。希ガス元素中ではヘリウムに次いで沸点・融点が低く、空気液化後の残存気体から加圧冷却、吸着などの操作によって精製される。単体は無色，無臭の単原子気体で，沸点－245.9℃，臨界温度－228.7℃，臨界圧 28.86気圧。化学的にきわめて安定。ガイスラー管で容易に放電し，赤色の輝線スペクトルを発するので，ネオン管用に広く使われている。低圧気体での放電によって赤色の輝線スペクトルを発し、他の希ガス気体あるいは水銀蒸気などとの混合気体での放電によってさまざまな色調の発光を示す。ネオンサイン、放電管、溶接保護ガスなどに利用される。
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解説
Ne．原子番号10の元素．電子配置[He]2s22p6の周期表18族希ガス元素の一つ．原子量20.1797(6)．質量数20(90.48(3)％)，21(0.27(1)％)，22(9.25(3)％)の3種の安定同位体と，質量数16～32，34の放射性同位体が知られている．ネオンは，1898年にW. Ramsay(ラムゼー)とM.W. Traversにより，液体空気中に発見され，ギリシア語の“新しい”を意味するνεοζ"(neos)から命名された．大気中に65000：1の割合で微量存在し，液体空気の分留により得られる．無色，無臭の気体．融点24.48 K，沸点27.10 K．臨界定数44.49 K，2.6786 MPa，0.48192 g mL－1．液体の密度1.2070 g cm－3(沸点)．蒸発熱(沸点)1.7326 kJ mol－1．第一イオン化エネルギー21.564 eV．化学的には不活性である．普通の意味の化合物はフッ化物を含め，まだ確認されていない．理論的にも存在は疑問視されている．低圧放電により赤橙色に強く光るので，ネオンサイン用にもっとも多く用いられる．そのほか，指示灯，電子管用充填ガス，冷媒などとして用いられる．森北出版「化学辞典（第2版）
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説明
In 1898, Dr William Ramsay and Morris M. Travers, a Scottish
scientist and a British scientist, respectively, discovered neon as
a condensation product in liquefied air, as in a process similar
to that used to collect neon today. Neon’s use in lighting
evolved from discoveries that gases under low pressure conduct
electricity. When some flowing electrons collide with residual
gas in an evacuated glass tube, the resulting ions emit light as
they return to their nonexcited state. The color of the light
depends on the residual gas; neon gas produces a red color and
argon, another inert gas often used in tubes (which are
frequently and incorrectly called neon lights), produces a blue
color. These two basic colors are often modified into many
different hues by the addition of such elements as mercury and
cadmium. The neon found on the Earth is considered to be
primordial in origin. Most of the neon is sequestered in the
Earth’s rocks or dissolved in water, with small amounts
escaping into the atmosphere during geologic weathering. The
escaped gas is slowly lost into space faster than it is replenished.
Consequently, neon constitutes only a small part (0.0018%) of
the Earth’s atmosphere, although this element is estimated to
be the fourth most abundant in the universe.
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化学的特性
Neon is an inert, colorless, odorless, tasteless
gas or liquid.
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物理的性質
Neon is a monatomic atom that is considered relatively inert. It does not even combinewith itself to form a diatomic molecule, as do some other gases (e.g., H2 and O2). Duringthe 1960s it was discovered that the noble gases are not really inert. Neon and the heaviernoble gases (Kr, Xe, and Rn) can form compounds when in an ionized state with some otherelements. For example, neon can form a two-atom ionized molecule of NeH+. Neon has alsobeen forced to form a compound with fluorine.
Neon’s melting point is –248.59°C, its boiling point is –246.08°C, and its density is0.0008999 g/cm3.
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同位体
There are a total of 11 isotopes of neon, three of which are stable. They are Ne-20, which makes up 90.48% of the natural abundance of neon on Earth; Ne-21, whichcontributes just 0.27% to all the neon found in nature; and Ne-22, which contributes9.25% to the natural abundance of neon. All the other isotopes have half-lives rangingfrom 3.746×10-21 seconds to 3.38 minutes.
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名前の由来
The word “neon” was derived from the Greek word neos, meaning
“new.”
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天然物の起源
Neon is the fourth most abundant element in the universe, but it makes up only 18.18ppm of the Earth’s atmosphere. It is the 82nd most abundant element on Earth.
Neon is believed to be produced by radioactive decay deep in the Earth. As it rises to thesurface, it escapes into the atmosphere and is soon dissipated. Some neon is found mixed withnatural gas and several minerals.
Neon is produced as a secondary product of the fractional distillation of liquid nitrogenand oxygen. Air is liquefied, and as it warms, nitrogen and oxygen boil off, leaving behindseveral other colder gases, including about 75% neon, which is then passed through activatedcharcoal to remove hydrogen and other gases.
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来歴
Discovered by Ramsay and Travers in 1898. Neon
is a rare gaseous element present in the atmosphere to the extent
of 1 part in 65,000 of air. It is obtained by liquefaction
of air and separated from the other gases by fractional distillation.
Natural neon is a mixture of three isotopes. Fourteen
other unstable isotopes are known. It is very inert element;
however, it is said to form a compound with fluorine. It is still
questionable if true compounds of neon exist, but evidence
is mounting in favor of their existence. The following ions
are known from optical and mass spectrometric studies: Ne+,
(NeAr)+, (NeH)+, and (HeNe+). Neon also forms an unstable
hydrate. In a vacuum discharge tube, neon glows reddish orange.
Of all the rare gases, the discharge of neon is the most
intense at ordinary voltages and currents. Neon is used in
making the common neon advertising signs, which accounts
for its largest use. It is also used to make high-voltage indicators,
lightning arrestors, wave meter tubes, and TV tubes.
Neon and helium are used in making gas lasers. Liquid neon
is now commercially available and is finding important application
as an economical cryogenic refrigerant. It has over 40
times more refrigerating capacity per unit volume than liquid
helium and more than three times that of liquid hydrogen. It is compact, inert, and is less expensive than helium when it
meets refrigeration requirements. Neon costs about $800/80
cu. ft. (2265 l).
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特性
As with the other noble gases, neon is colorless, tasteless, and odorless. It glows bright redwhen electricity is passed through it in an enclosed glass tube. It will turn from a gas to a liquidat –245.92°C, and only under great pressure will it become solid. It is noncombustible andlighter than air, but not as light as helium.
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使用
Gas in neon light tubes; ingredient of gaseous fillers for antifog devices, warning signals, electrical current detectors, high-voltage indicators for high-tension electric lines, lightning arresters, wave-meter tubes; in Ne-He lasers; in mixtures with He and Ar in Geiger counters. Liquid as cryogen to produce low temperetures.
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定義
An inert colorless odorless
monatomic element of the rare-gas group.
Neon forms no compounds. It occurs in
minute quantities (0.0018% by volume) in
air and is obtained from liquid air. It is
used in neon signs and lights, electrical
equipment, and gas lasers.
Symbol: Ne; m.p. –248.67°C; b.p.
–246.05°C; d. 0.9 kg m–3 (0°C); p.n. 10;
r.a.m. 20.18.
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一般的な説明
A colorless odorless noncombustible gas. Chemically inert. The vapors are lighter than air. Nontoxic, but can act as a simple asphyxiant. Exposure of the container to prolonged heat or fire may cause NEON to rupture violently and rocket. Principal use is to fill lamp bulbs and tubes.
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反応プロフィール
These substances undergo no chemical reactions under any known circumstances. They are nonflammable, noncombustible and nontoxic. They can asphyxiate.
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危険性
Neon is nontoxic. As an asphyxiate gas, it can smother by removing oxygen from thelungs.
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健康ハザード
Vapors may cause dizziness or asphyxiation without warning. Vapors from liquefied gas are initially heavier than air and spread along ground.
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火災危険
Non-flammable gases. Containers may explode when heated. Ruptured cylinders may rocket.
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安全性プロファイル
An inert asphpant gas.
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職業ばく露
Neon is used in photoelectric bulbs
and certain light tubes; in the electronic industry; in lasers;
in plasma studies; and other research.
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輸送方法
UN1065 Neon and UN1913 Neon, refrigerated
liquid (cryogenic liquid), Hazard Class: 2.2; Labels:
2.2-Nonflammable compressed gas. Cylinders must be
transported in a secure upright position, in a well-ventilated
truck. Protect cylinder and labels from physical damage.
The owner of the compressed gas cylinder is the only entity
allowed by federal law (49CFR) to transport and refill
them. It is a violation of transportation regulations to refill
compressed gas cylinders without the express written
permission of the owner.
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純化方法
Pass the gas through a copper coil packed with 60/80 mesh 13X molecular sieves which is cooled in liquid N2, or through a column of Ascarite (NaOH-coated silica adsorbent).
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不和合性
Compressed neon gas under pressure
may explode when heated.
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廃棄物の処理
Return refillable compressed
gas cylinders to supplier. Venting to atmosphere.
