Okay, helium balloons room light...but they"re no that light! The fanciful image below serves to make the allude that helium is one of the lightest elements. Helium belongs to a group of facets called the noble gases.

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Figure (PageIndex1): Helium is just one of the lightest facets in the routine table.

What are Noble Gases?

Noble gases are nonreactive, nonmetallic elements in group 18 of the periodic table. Together you have the right to see in the regular table in the number below, noble gases include helium (left( ceHe ight)), neon (left( ceNe ight)), argon (left( ceAr ight)), krypton (left( ceKr ight)), xenon (left( ceXe ight)), and also radon (left( ceRn ight)). All noble gases room colorless and also odorless. They also have short boiling points, which describes why they are all gases in ~ room temperature. Radon, in ~ the bottom the the group, is radioactive, so the constantly decays to various other elements.

Figure (PageIndex2): Noble gases space in team 18 of the routine table, in this situation the red obelisk on the much right.

mmsanotherstage2019.comical properties of Noble Gases

Noble gases room the the very least reactive the all known elements. Your outer power levels room full due to the fact that they each have actually eight valence electrons. The only exception is helium, which has actually just 2 electrons. However helium likewise has a complete outer energy level, since its only power level (energy level 1) deserve to hold a preferably of 2 electrons. A full outer energy level is the most stable arrangement of electrons. Together a result, noble gases can not become much more stable by reaction with other elements and also gaining or shedding valence electrons. Therefore, noble gases space rarely affiliated in mmsanotherstage2019.comistry reactions and almost never form compounds with other elements.

Noble Gases and also the Octet Rule

Because the noble gases space the least reactive of every elements, their eight valence electron are used as the standard for non-reactivity, and to explain how other facets interact. This is proclaimed as the octet ("group of eight") rule. According to this rule, atoms reaction to form compounds that enable them to have a team of eight valence electrons favor the noble gases. Because that example, salt (with one valence electron) reacts with chlorine (with seven valence electrons) to kind the stable compound sodium chloride (table salt). In this reaction, sodium donates one electron and also chlorine accepts it, providing each aspect an octet of valence electrons.

Some uses of Noble Gases

Have you ever hadhelium balloons choose those in the elephant image? uneven a balloon filled through air, a balloon filled v helium requirements to be weighted under so that it won"t float away—although friend don"t have to use an elephant!

Early incandescent light bulbs, favor the one pictured in the number below, didn"t last an extremely long. The filaments quickly burned out. Return air was pumped the end of the bulb, that wasn"t a finish vacuum. Oxygen in the little amount of air staying inside the light pear reacted through the steel filament. This corroded the filament and also caused dark shop on the glass. Pour it until it is full a irradiate bulb with argon gas prevents these problems. That"s why modern-day light bulbs room filled with argon.

Figure (PageIndex3): modern light bulbs are filled v the noble gas argon to protect against corrosion that the filament inside.

Noble gases are also used to fill the glass tubes of lighted indicators like the one in the number below. Return noble gases room mmsanotherstage2019.comically nonreactive, their electrons have the right to be energized by sending an electric existing through them. As soon as this happens, the electrons run to a higher energy level. Once the electrons return to their original energy level, they provide off energy as light. Various noble gases give off irradiate of various colors. Neon gives off a reddish-orange light, prefer the native "Open" in the sign below. Krypton gives off violet light and xenon gives off blue light.

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Figure (PageIndex4): indicators like this one space filled through nobles gases choose neon or xenon, which offer off light when energized.