noble gases

chemical properties of noble gases

Noble gases are the least reactive of all known elements. Thats because with eight valence electrons, their outer energy levels are full. The only exception is helium, which has just two electrons. But helium also has a full outer energy level, because its only energy level (energy level 1) can hold a maximum of two electrons. A full outer energy level is the most stable arrangement of electrons. As a result, noble gases cannot become more stable by reacting with other elements and gaining or losing valence electrons. Therefore, noble gases are rarely involved in chemical reactions and almost never form compounds with other elements.

what are noble gases

Noble gases are nonreactive, nonmetallic elements in group 18 of the periodic table. As you can see in the periodic table below, noble gases include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). All noble gases are colorless and odorless. They also have low boiling points, explaining why they are gases at room temperature. Radon, at the bottom of the group, is radioactive, so it constantly decays to other elements. Click image to the left or use the URL below. URL: Q: Based on their position in the periodic table (Figure 1.1), how many valence electrons do you think noble gases have? A: The number of valence electrons starts at one for elements in group 1. It then increases by one from left to right across each period (row) of the periodic table for groups 1-2 and 13-18 (numbered 3-0 in the table above). Therefore, noble gases have eight valence electrons.

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some uses of noble gases

Did you ever get a birthday balloon like the one pictured 1.2? The balloon is filled with the noble gas helium. The gas is pumped from a tank into a Mylar balloon. Unlike a balloon filled with air, a balloon filled with helium needs to be weighted down so it wont float away. Q: Why does a helium balloon float away if its not weighted down? A: Helium atoms have just two protons, two neutrons, and two electrons, so they have less mass than any other atoms except hydrogen. As a result, helium is lighter than air, explaining why a helium balloon floats up into the air unless weighted down. Early incandescent light bulbs, like the one pictured in the Figure 1.3, didnt last very long. The filaments quickly burned out. Although air was pumped out of the bulb, it wasnt a complete vacuum. Oxygen in the small amount of air remaining inside the light bulb reacted with the metal filament. This corroded the filament and caused dark deposits on the glass. Filling a light bulb with argon gas prevents these problems. Thats why modern light bulbs are filled with argon. A: As a noble gas with eight electrons, argon doesnt react with the metal in the filament. This protects the filament and keeps the glass blub free of deposits. Noble gases are also used to fill the glass tubes of lighted signs like the one in the Figure 1.4. Although noble gases are chemically nonreactive, their electrons can be energized by sending an electric current through them. When this happens, the electrons jump to a higher energy level. When the electrons return to their original energy level, they give off energy as light. Different noble gases give off light of different colors. Neon gives off reddish-orange light, like the word Open in the sign below. Krypton gives off violet light and xenon gives off blue light.

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noble gases and the octet rule

Because the noble gases are the least reactive of all elements, their eight valence electrons are used as the standard for nonreactivity and to explain how other elements interact. This is stated as the octet (group of eight) rule. According to this rule, atoms react to form compounds that allow them to have a group of eight valence electrons like the noble gases. For example, sodium (with one valence electron) reacts with chlorine (with seven valence electrons) to form the stable compound sodium chloride (table salt). In this reaction, sodium donates an electron and chlorine accepts it, giving each element an octet of valence electrons.

instructional diagrams

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questions

noble gases are the elements in group 17 of the periodic table.

a. true

-->  b. false

noble gases are nonreactive elements.

-->  a. true

b. false

noble gases include

a) oxygen.

b) nitrogen.

-->  c) argon.

d) all of the above

all noble gases are

a) odorless.

b) colorless.

c) radioactive.

-->  d) two of the above

noble gases have high boiling points.

a. true

-->  b. false

diagram questions

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