Okay, helium balloons space light...but they"re no that light! The cool image listed below serves to make the point that helium is among the lightest elements. Helium belongs to a team of elements called the noble gases.

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

What room Noble Gases?

Noble gases space nonreactive, nonmetallic facets in team 18 the the periodic table. As you can see in the routine table in the figure below, noble gases encompass 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 space colorless and odorless. They also have short boiling points, which explains why they are all gases at room temperature. Radon, in ~ the bottom that the group, is radioactive, so that constantly decays to various other elements.

Figure (PageIndex2): Noble gases space in team 18 of the regular table, in this instance the red column on the much right.

cg-tower.comical nature of Noble Gases

Noble gases are the the very least reactive that all recognized elements. Their outer power levels space full since they each have actually eight valence electrons. The only exemption is helium, which has just 2 electrons. However helium likewise has a full outer energy level, due to the fact that its only power level (energy level 1) deserve to hold a maximum of two electrons. A full outer power level is the many stable arrangement of electrons. As a result, noble gases cannot become more stable by reaction with various other elements and gaining or shedding valence electrons. Therefore, noble gases space rarely involved in cg-tower.comistry reactions and almost never form compounds with various other elements.

Noble Gases and the Octet Rule

Because the noble gases room the the very least reactive of every elements, your eight valence electrons are offered as the conventional for non-reactivity, and also to explain how other aspects interact. This is proclaimed as the octet ("group the eight") rule. According to this rule, atoms react to form compounds that permit them to have a team of eight valence electrons like the noble gases. For example, salt (with one valence electron) reacts through chlorine (with 7 valence electrons) to type the steady compound sodium chloride (table salt). In this reaction, salt donates one electron and also chlorine accepts it, giving each element an octet the valence electrons.

Some provides of Noble Gases

Have you ever before hadhelium balloons favor those in the elephant image? unlike a balloon filled v air, a balloon filled with helium demands to it is in weighted down so that it won"t to rise away—although friend don"t need to use an elephant!

Early incandescent light bulbs, favor the one pictured in the figure below, didn"t last very long. The filaments quickly burned out. Return air to be pumped the end of the bulb, the wasn"t a finish vacuum. Oxygen in the small amount the air remaining inside the light bulb reacted through the metal filament. This corroded the filament and caused dark deposits on the glass. Filling a irradiate bulb through argon gas stays clear of these problems. That"s why modern light bulbs room filled through argon.

Figure (PageIndex3): contemporary light bulbs room filled with the noble gas argon to protect against corrosion of the filament inside.

Noble gases are also used to to fill the glass pipe of lighted signs like the one in the figure below. Although noble gases room cg-tower.comically nonreactive, their electrons have the right to be energized by sending out an electric present through them. Once this happens, the electrons run to a greater energy level. As soon as the electrons go back to their original energy level, they give off power as light. Various noble gases give off light of different colors. Neon gives off a reddish-orange light, favor the word "Open" in the sign below. Krypton offers off violet light and also xenon offers off blue light.

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Figure (PageIndex4): indications like this one room filled through nobles gases prefer neon or xenon, which provide off light when energized.