Noble gases



Noble Gases 2857
Photo by: photo-dave

The noble gases are the six elements that make up Group 18 of the periodic table: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). At one time, this family of elements was also known as the rare gases. Their present name comes from the fact that the six gases are highly unreactive; they appear almost "noble"—above interacting with other members of the periodic table. This lack of reactivity has also led to a second name by which they are sometimes known—the inert gases. (Inert means inactive.)

Abundance and production

As their former name suggests, the noble gases are rather uncommon on Earth. Collectively, they make up about 1 percent of Earth's atmosphere. Most of the noble gases have been detected in small amounts in minerals found in Earth's crust and in meteorites. They are thought to have been released into the atmosphere long ago as by-products of the decay of radioactive elements in Earth's crust. (Radioactivity is the property that some elements have of spontaneously giving off energy in the form of particles or waves when their nuclei disintegrate.)

Of all the rare gases, argon is present in the greatest amount. It makes up about 0.9 percent by volume of Earth's atmosphere. The other noble gases are present in such small amounts that it is usually more convenient to express their concentrations in terms of parts per million (ppm). The concentrations of neon, helium, krypton, and xenon are, respectively, 18 ppm, 5 ppm, 1 ppm, and 0.09 ppm. For example, there are only 5 liters of helium in every million liters of air. By contrast, helium is much more abundant in the Sun, stars, and outer space. In fact, next to hydrogen, helium is the most abundant element in the universe. About 23 percent of all atoms found in the universe are helium atoms.

Radon is present in the atmosphere in only trace amounts. However, higher levels of radon have been measured in homes around the United States. Radon can be released from soils containing high concentrations of uranium, and they can be trapped in homes that have been weather sealed to make heating and cooling systems more efficient. Radon testing

Lead canisters used to store xenon for medical diagnostic purposes. (Reproduced by permission of Photo Researchers, Inc.)
Lead canisters used to store xenon for medical diagnostic purposes. (Reproduced by permission of
Photo Researchers, Inc.
)

kits are commercially available for testing the radon content of household air.

Most of the rare gases are obtained commercially from liquid air. As the temperature of liquid air is raised, the rare gases boil off from the mixture at specific temperatures and can be separated and purified. Although present in air, helium is obtained commercially from natural gas wells where it occurs in concentrations of between 1 and 7 percent of the natural gas. Most of the world's helium supplies come from wells located in Texas, Oklahoma, and Kansas. Radon is isolated as a product of the radioactive decay of radium compounds.

Properties

The noble gases are all colorless, odorless, and tasteless. They exist as monatomic gases, which means that their molecules consist of a single atom apiece. The boiling points of the noble gases increase in moving down the periodic table. Helium has the lowest boiling point of any element. It boils at 4.215 K (−268.93°C). It has no melting point because it cannot be frozen at any temperature.

The most important chemical property of the noble gases is their lack of reactivity. Helium, neon, and argon do not combine with any other elements to form compounds. It has been only in the last few decades that compounds of the other rare gases have been prepared. In 1962 English chemist Neil Bartlett (1932–) succeeded in preparing the first compound of a noble gas, a compound of xenon. The compound was xenon platinofluoride (XePtF 6 ). Since then, many xenon compounds containing mostly fluorine or oxygen atoms have also been prepared. Krypton and radon have also been combined with fluorine to form simple compounds. Because some noble gas compounds have powerful oxidizing properties, they have been used to synthesize other compounds.

The low reactivity of the noble gases can be explained by their electronic structure. The atoms of all six gases have outer energy levels containing eight electrons. Chemists believe that such arrangements are the most stable arrangements an atom can have. Because of these very stable arrangements, noble gas atoms have little or no tendency to gain or lose electrons, as they would have to do to take part in a chemical reaction.

Uses

As with all substances, the uses to which the noble gases are put reflect their physical and chemical properties. For example, helium's low density and inertness make it ideal for use in lighter-than-air craft such as balloons and dirigibles (zeppelins). Because of the element's very low boiling point, it has many applications in low-temperature research and technology. Divers breathe an artificial oxygen-helium mixture to prevent the formation of gas bubbles in the blood as they swim to the surface from great depths. Other uses for helium have been in supersonic wind tunnels, as a protective gas in growing silicon and germanium crystals and, together with neon, in the manufacture of gas lasers.

Neon is well known for its use in neon signs. Glass tubes of any shape can be filled with neon. When an electrical charge is passed through the tube, an orange-red glow is emitted. By contrast, ordinary incandescent lightbulbs are filled with argon. Because argon is so inert, it does not react with the hot metal filament and prolongs the bulb's life. Argon is also used to provide an inert atmosphere in welding and high-temperature metallurgical processes. By surrounding hot metals with inert argon, the metals are protected from potential oxidation by oxygen in the air.

Krypton and xenon also find commercial lighting applications. Krypton can be used in incandescent lightbulbs and in fluorescent lamps. Both are also employed in flashing stroboscopic lights that outline commercial airport runways. And because they emit a brilliant white light when electrified, they are used in photographic flash equipment. Due to the radioactive nature of radon, it has medical applications in radiotherapy.

[ See also Element, chemical ; Periodic table ]



Also read article about Noble Gases from Wikipedia

User Contributions:

1
charlee
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Mar 10, 2008 @ 6:18 pm
this is a very good article. I am in 8th grade and we are doing a report about a element from the periodic table and i chose Neon. your article helped me alot to find information and in a way that i can understand it...
thank you,

Charlee
2
Scott
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Jun 19, 2008 @ 1:13 pm
Some other uses for noble gases: Ar is used for optical and mass spectrometry as the plasma gas. Other noble gases are used for plasma spectrometry including He for improved detection limits of Cl. Current studies are being conducted to see if there are improved detection limits for any other elements on the periodic table with the use of other noble gases like Ne, Kr and Xe. The problem with Kr and Xe is that they r so darn expensive!!!!!
3
chris
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Sep 28, 2008 @ 9:21 pm
Grear article!!!!! i am also doing a project on the noble gases for my AP chemistry classand this was a lifesaver!!!!
4
Leila
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Oct 9, 2008 @ 8:20 pm
Wow, your site was a life-saver!
Last minute extra credit project, and I got all my answers here! :]]

Thanks!
5
A
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May 4, 2009 @ 5:17 pm
im making a mobile on the atomic structure of neon and giving a speech on facts about neon. I also found your website very helpful.

-A
6
Sanah
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Jun 7, 2009 @ 6:06 am
This was a very helpful site. I was doing my assignment on helium. It told me some really good info. Especially about the uses and how they relate to heliums properties :)
7
larry
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Sep 7, 2009 @ 10:22 pm
thanks. . .. . .this website is so vey good!and i like this website...again thanks!
8
L. Kate Downey
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Nov 6, 2009 @ 1:13 pm
This site was a great help for my slides me and my partner are doing a keynote on (Nonmetals-noble gasses- ) thanks for the information
9
lilly
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Jan 18, 2010 @ 4:16 pm
thanx for all the info. I am doing a project on neon and this has totally helped me out and has saved my grade. thanx again
10
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Feb 18, 2010 @ 10:22 pm
all noble gases have melting points but other info is very useful
11
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Mar 15, 2010 @ 9:09 am
I cant belive this is what some of the noble gases are used for...
12
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Apr 21, 2010 @ 6:18 pm
Lifesaver 4 AP Class! Interesting facts, I 2 can't belive this stuff! Very Useful!
13
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Apr 29, 2010 @ 6:06 am
does xenon have six energy levels? i need to know so i can pass this really gross chemistry crap.. thank you!
14
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Apr 30, 2010 @ 7:19 pm
How is argon prepared or extracted in the purest form?
15
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May 3, 2010 @ 11:11 am
This is a very good website. I'm doing a report on Noble Gases in my science class and got all the detail I needed. Lets just hope I pass this class! :D
16
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May 30, 2010 @ 1:13 pm
this article helped me so much. i spent so much time searching for a website that would help me find the uses for noble gases and i finally found it. thank you.
17
sweetu
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Aug 12, 2010 @ 9:21 pm
I really like this article. I have never thought that the noble gases are not so common on Earth and that they have so many uses and properties,this article has shown me alot of facts and easier explainations so when i'm studying I have alot to work with. THANKS!!!
18
h&t
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Sep 27, 2010 @ 11:11 am
We are doing a project on everything about Noble gases. This site helped. Thanks(:
19
Evelyn
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Oct 20, 2010 @ 3:15 pm
Wow, thos articel is very useful. I was doing a research on noble gases and it has so much info! thnx:)
20
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Nov 5, 2010 @ 11:11 am
I love this site. Itn has every thing i need for my science report on noble gases
21
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Nov 6, 2010 @ 11:23 pm
I'LIKE THIS ARTICLE VERY HELP ME FOR MY WORK SO THANK'S
22
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Nov 8, 2010 @ 4:04 am
why helium is presents in low concentration in the atmosphere even though it is the second most abundant element in the universe?please answer my question, thx a lot :)
23
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Apr 15, 2011 @ 5:05 am
Due to it high power of fog penetration neon is used in aerodrome beacons
24
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Sep 28, 2011 @ 2:14 pm
i love this programme very very much ilove all ossa students (science 2)
25
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Sep 30, 2011 @ 8:20 pm
swagg and thanks this helped me on my project
Chemistry
26
Madison
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Oct 3, 2011 @ 5:17 pm
this was helpful thanks bunches it was fresh i have a project
27
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Oct 7, 2011 @ 11:11 am
i love this site it has everything your looking for in gases and element i love my science teacher Mrs. Hutchison from Highlands Middle School
28
Goodluck amadi
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Mar 22, 2012 @ 12:12 pm
Pls wat element in the noble gas group has a high power of fog penetration used in aerodrome beacons?
29
Orlhatundji
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Feb 20, 2014 @ 4:16 pm
@muyash. . . From this article, Helium is present in abundance in outer space, sun and stars. . .but not in the earth's atmosphere. . Thank you Tosin Ayodele for the use of Neon in Aerodrome beacon, it helped me in answering a Jamb question. Kudos to this article.
30
chomo
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Oct 8, 2014 @ 11:11 am
great info with lots of intersting facts and i hope it will help you guys too.
31
afishat
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Jan 2, 2015 @ 2:14 pm
the stability of noble gases are due to the fact that they? please that's a question
32
john1th
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Nov 26, 2015 @ 6:06 am
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33
john1th
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Nov 26, 2015 @ 6:06 am
Thank you this is an amazing website I thank you very much for making this you have helped so many children with your work and I love you
34
pinkprincess
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Nov 26, 2015 @ 7:07 am
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35
ginger1234
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Nov 26, 2015 @ 7:07 am
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36
pinkprincess
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Nov 26, 2015 @ 7:07 am
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37
The Arch Bishop Of Canterbury
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Nov 26, 2015 @ 7:07 am
This website is utterly incredible all of this has helped me with my noble gasses classwork with miss hayes, so I just want to thank you so much. yours sincerely the arch bishop of Canterbury.
38
ginger1234
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Nov 26, 2015 @ 7:07 am
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39
anto
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May 10, 2016 @ 2:02 am
wow this site is amaizing it help me do a project i thank u so very much it has help me and other pple
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40
ashley
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May 31, 2016 @ 12:00 am
Im also in 8th grade and this site helped me out alot doing my homwwork.
41
Elizabeth
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Mar 19, 2017 @ 3:15 pm
Thanks
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