Name that element!

It puts the color in fireworks and takes the danger our of icy roads. It helps digest your food and gives clues to the Martian past. Can you name that element? Follow these eight clues to find out. Then turn the page to test your chemistry IQ.

(CLUE 1)

TEAM PLAYER

By itself, the mystery element is a smelly, greenish-yellow poisonous gas. Luckily, it rarely goes solo in nature. The smallest unit of this element, or its atom, is very unstable, so it's quick to join with other elements to form compounds (two or more elements that are chemically combined). Many of these compounds are not poisonous; they are even vital to living things. Trillions of tons of this mystery element is in the oceans.

GOT IT ALREADY? SCORE 100 POINTS. IF NOT, READ CLUE #2.

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(CLUE 2)

ROCKIN' MARS

Was the Red Planet always a rocky, frozen wasteland? Last year, two NASA rovers caused a stir when they identified high levels of the mystery element in Martian rocks. "[The element] is very soluble (dissolvable) in water, and the abundance: indicates that these rocks probably were affected by liquid water long ago," explains Joy Crisp, a rover mission scientist. That's one huge clue for scientists trying to understand Mars's geologic history.

NABBED THE ANSWER? SCORE 80 POINTS. STILL GUESSING? GO TO THE NEXT CLUE.

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(CLUE 3)

SHAPE SHIFTER

The mystery element is everywhere: in plumbing pipes, gym bags, and even your most fashionable shoes. A compound made of this element, carbon, and hydrogen forms a multipurpose material called vinyl. Besides being versatile, vinyl is strong and fire-resistant. It's also easy to recycle--the thermoplastic (material that becomes soft when heated and rigid when cooled) can be reshaped into other products.

GAME OVER ALREADY? SCORE 60 POINTS. STILL PLAYING? CHECK OUT CLUE #4.

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(CLUE 4)

STOMACH THIS

Add one part of hydrogen to one part of this element and you'll get an acid that is so corrosive it can eat rust off the surface of steel. Believe it or not, your stomach lining produces the same acid. The acid activate enzymes (proteins that speed up chemical reactions) that digest your lunch. Why doesn't the acid eat holes in your stomach? Your stomach lining defends itself by making antacids, or acid-fighting agents.

NAME IT NOW? SCORE 40 POINTS. OTHERWISE, READ ON.

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(CLUE 5)

LIGHT SHOW

This nonmetal combines with three different metals to make compounds that put the red, blue, or green in fireworks. The compounds are volatile--they turn easily into gases when heated. As fireworks burn, the gases' electrons (negatively charged particles) absorb energy from the heat; then, they release that energy as a colorful flash. Each compound's gases produce a different-hued light. "Without [this element] you wouldn't get vivid colors," says John Conkling, a chemistry professor at Washington College.

HIT ON THE ANSWER? SCORE 20 POINTS. IF NOT, KEEP TRYING!

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(CLUE 6)

SLUSHY 

When water cools to below 0[degrees]C (32[degrees]F)--or its freezing point (temperature at which a liquid turns to a solid)--it hardens into ice. This spells slippery roads on wet winter days, Road crews come to the rescue by scattering a compound made of calcium and the mystery element onto wet roads. When the compound dissolves in the water, it helps keep the liquid from freeing: Conkling explains: The more solids you dissolve into water, the lower its freezing point.

SCORE 10 POINTS IF YOU HAVE THE ELEMENT WITH THE HELP OF SIX CLUES. STILL GUESSING? READ ON.

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(CLUE 7)

UNDER PRESSURE

A gas containing this element and fluorine--a member of the same group (column) on the periodic table--once gave hair sprays pumping power. But the gas was banned in many countries in the 1980s because it damages the ozone layer (protective gas in the upper atmosphere): When the gas molecules rise upward, they split apart. This releases the mystery element's reactive (combines easily with others) atoms, which destroy ozone molecules by bonding with their atoms.

GUESS THE ELEMENT? SCORE 5 POINTS. IF NOT, TRY your LAST CLUE.

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(CLUE 8)

If not for the mystery element, your local pool might be a slimy, clouding breeding ground for germs. The element, when combined with calcium and oxygen, becomes a powerful water disinfectant, or germ killer--just one to four parts of it for every million parts of pool water will do the job! Higher levels can harm swimmers. Hint: This element has 17 electrons.

GAME'S OVER. NOW TURN TO PAGE 22.

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Anatomy of an Element

x--Atomic number

??--Element symbol

Name--Element name

X.XXXX--Average atomic mass 

KEY DEFINITIONS:

ATOMIC NUMBER equals the number of protons (positively charged particles) in an atom's nucleus, or center. Every element contains a different number of protons, and so has a unique atomic number. In a neutral atom, the number of protons and the number of electrons (negatively charged particles) are equal.

ATOMIC MASS equals the number of protons plus the number of neutrons (uncharged particles) found in a single atom of an element. The atom's mass is in its nucleus, which houses both protons and neutrons.

DID YOU KNOW?

* The word "chlorine" comes from the Greek word "chloros," which means greenish yellow--the same color as the element when it is in its pure, gassy form.

* Chlorine is the 20th most abundant element found in Earth's crust. It also makes up 1.8 percent of seawater.

* Certain species of tree frogs have toxin on their skin, which helps them ward off predators (see "I Make a Killer Potion," SW 1/03/2005). This poison contains a chlorine compound.

CRITICAL THINKING:

* For almost a century, chlorine has been widely used to clean drinking water. How does the cleanliness of local drinking water affect a community? (For information, see: www.waterandhealth.org/drinkingwater/wp.html)

CROSS-CURRICULAR CDNNECTIONS:

ART: Research the characteristics and behavior of chlorine. Then, create and illustrate a comic strip. Have both the superhero and the villain use a chlorine-related property as their chief secret power. (For help, see resources below.)

RESOURCES:

* For fun facts and classroom activities about chlorine, visit: www.science-education.org/

* How are comic-book; superheroes related to the periodic table of the ements? Find out at this university of Kentucky Web site: www.uky.edu/Projects/Chemcomics/

DIRECTIONS: On a separate piece of paper, defend or dispute the following statements. (Hint: Defend means to explain why a statement is correct. Dispute means to explain why a statement is incorrect.)

1. Chlorine, in its pure form, is commonly found in nature.

2. A long time ago, there may have been liquid water on Mars.

3. During the winter, a compound made up of calcium and chlorine helps keep motorists safe.

4. A gas containing chlorine and fluorine are comraonly found in hairspray cans.

1. Dispute: Chlorine, in its pure form, is rarely found in nature. That's because its atom is very unstable. This reactive atom is quick to join other elements to form compounds.

2. Defend: Last year, two NASA rovers caused a stir when they identified high levels of chlorine in Martian rocks. Because chlorine is very soluble in water, the abundance indicates that these rocks probably were affected by liquid water long ago.

3. Defend: Water has a freezing point of 0[degrees]C (32[degrees]F). At that temperature and below, it harclens into ice. This spells slippery roads on wet winter days. Road crews come to the rescue by spreading a chlorine compound into the water on roads. When the compound dissolves, it helps keep the liquid from freezing. That's because the more solids you dissolve into water, the lower the water's freezing point.

4. Dispute: This gas has been banned in many countries since the 1980s. Scientists discovered that the gas damages the ozone layer. When the gas molecules rise to the upper atmosphere, they sptit apart. This releases ohlodne's reactive atoms, which destroy ozone molecules by bonding with their atoms.

VOCABULARY BUILDER

IT'S ELEMENTAL!

Name: --

Directions: First, read "Name That Element!" (p. 20). Then, solve the clues below to complete this crossword puzzle. To spell out the bonus words, unscramble the letters in parentheses.

ACROSS

1. --(--)-- are acid-fighting agents.

2 --(--)-- are proteins that speed up chemical reactions.

3. The --(--)-- layer is a protective layer of gas in the upper atmosphere.

4. Chlorine, in its pure form, is a smelly, greenish-yellow --(--)-- gas.

5. A --(--)--(--)-- is used to kill germs.

6. Some acids are so --(--)--(--), they can eat the rust off metal surfaces.

DOWN

7. --(--)-- are two or more elements that are chemically combined.

8. Elements of the same --(--) belong to the same column on the periodic table.

9. --(--)-- is a material that becomes soft when heated and rigid when cooled.

10. --(--)-- means dissolvable in water.

11. When heated, a (--)--(--)-- material turns easily into gases.

12. A (--)-- atom is an atom that easily combines with other atoms.

BONUS:

A chlorine compound in this protective garment helps protect crime fighters:

a. -- b. --

1. antacids 2. enzymes 3. ozone 4. poisonous 5. disinfectant 6. corrosive 7. compounds 8. group 9. thermoplastic 10. soluble 11. volatile 12. reactive Bonus: a. bulletproof b. vest