Uses for the Noble Gases The “neon” lights you see in advertising signs, like the one in Figure 12, can contain any of the noble gases, not just neon. Electricity is passed through the glass tubes that make up the sign. These tubes contain the noble gas, and the electricity causes the gas to glow. Each noble gas produces a unique color. Helium glows yellow, neon glows red-orange, and argon produces a bluish-violet color.
Figure 12 Noble gases are used in many applications. Scientists use helium balloons to measure atmos- pheric conditions.
Argon, the most abundant of the noble gases on Earth, was first found in 1894. Krypton is used with nitrogen in ordinary lightbulbs because these gases keep the glowing filament from burning out. When a mixture of argon, krypton, and xenon is used, a bulb can last longer than bulbs that do not contain this mix- ture. Krypton lights are used to illuminate land- ing strips at airports, and xenon is used in strobe lights and was once used in photographic flash cubes.
At the bottom of the group is radon, a radioactive gas pro- duced naturally as uranium decays in rocks and soil. If radon seeps into a home, the gas can be harmful because it continues to emit radiation. When people breathe the gas over a period of time, it can cause lung cancer.
Each noble gas glows a different color when an electric current is passed through it.
Why are noble gases used in lights?
Groups 1 and 2
Groups 1 and 2 elements are always com- bined with other elements.
The elements in Groups 1 and 2 are all metals except for hydrogen.
Alkaline earth metals are not as active as the alkali metals.
With Groups 13–18, a single group can con- tain metals, nonmetals, and metalloids.
Nitrogen and phosphorus are required by liv- ing things.
The halogen group will form salts with alkali metals.
Compare and contrast the elements in Group 1 and the elements in Group 17.
Describe two uses for a member of each representative group.
Identify the group of elements that does not readily combine with other elements.
Think Critically Francium is a rare radioactive alkali metal at the bottom of Group 1. Its properties have not been studied carefully. Would you predict that francium would combine with water more or less readily than cesium?
5. Predict how readily astatine would form a salt com- pared to the other elements in Group 17. Is there a trend for reactivity in this group?
SECTION 2 Representative Elements K ◆
(l)file photo, (r)Bill Freund/CORBIS