Name that element!

This element Explodes on contact With water. It Can save lives. And it helps Athletes recover from a Tough workout. Can you name that element? Grab a periodic table (next page) and follow these eight clues to figure out the answer. Then flip the page to test your chemistry IQ.

CLUE 1

LIKE BUTTER

Like all metals, the mystery element's pure form is shiny, conducts heat and electricity, and is solid at room temperature. But unlike most metals, the silvery element is as soft as a stick of butter. It can easily be cut with a knife.

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

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CLUE 2

STARGAZER

This alkali metal helps city stargazers see the night sky better. Bright white streetlights cast a glow over a city, making it hard to see the stars. But lights that burn this element cast a softer, yellow glow. "It's easier on astronomers' eyes--the lamps don't cause as much light pollution," says professor Eric Betterton, of the University of Arizona.

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

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CLUE 3

SAFETY FEATURE

This element, a member of the hydrogen family, may save your life in a car crash. When a collision triggers air-bag sensors, toxic pills made of nitrogen and the mystery element explode. The reaction releases harmless nitrogen gas, which fills the air bag at a speed of up to 322 kilometers (200 miles) per hour, "But manufacturers are phasing [the pills] out because of their toxicity," says Betterton.

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

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CLUE 4

FIREFIGHTER

Fire extinguishers spray foam loaded with the carbonate (combined with carbon and oxygen) form of the mystery element, also known as baking soda, At high temperatures, baking soda releases carbon dioxide gas. The gas and foam from an extinguisher rob a fire of its oxygen and smother the flames.

NAME IT NOW, SCORE 40 POINTS.

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CLUE 5

SINK OR SWIM

Freshwater fish expend a boatload of energy pumping ions (atoms that have gained or lost electrons) of the element from the surrounding water through their gills. The element prevents too much water from entering the fish's body. "Otherwise, the fish is in danger of exploding," says Bob Murray of the Gatorade Sports Science Institute. (Hint: An ion of this element has the same number of electrons as neon.)

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

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CLUE 6

POWER AID

As an ingredient in most sports drinks, this element helps you power up after a tough workout. That's because the mystery element is an electrolyte (substance that forms ions in water) dissolved in most of your body's fluids, including sweat. "When you're sweating a lot, sports drinks deliver what plain water can't--they replenish the electrolytes lost in sweat," says Murray. This element most often loses one electron to become positively charged.

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

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CLUE 7

DESERT DABBLER

In nature, this element is always found in compounds of two or more elements, It most commonly hooks up with halogens (elements in Group 17 on the periodic table), When combined with chlorine, it forms the mineral halite. In the U.S., chunks of halite can be spotted in southwestern deserts after water evaporates from inland lakes.

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

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CLUE 8

FRIES WITH THAT

Your favorite snacks just wouldn't taste the same without this element, which has an atomic mass of nearly 23 atomic mass units (u). It's one of 25 elements essential to your diet. But too much pigging out on this element may lead to high blood pressure. The American Heart Association recommends eating no more than 2,400 milligrams (less than one ounce) of the element each day.

STILL NO ANSWER? TURN TO PAGE 20.

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IT'S YOUR CHOICE Test your chemistry IQ! Answer the following questions about elements and the periodic table.

1. Name that element!

2. Metals farther to the right side of each period in the table tend to conduct electricity better than those on the left side. And most nonmetals don't conduct electricity. Which of the following has a greater conductivity than nickel (Ni)?

A Titanium (Ti)

B Bromine (Br)

C Gallium (Ga)

D Potassium (K)

3. If barium (Ba) loses two electrons, it will contain the same number of electrons as which element on the table?

A Hafnium (Hf)

B Xenon (Xe)

C Cesium (Cs)

D Calcium (Ca)

4. An ion is defined as

A a positively charged particle.

B a negatively charged particle.

C a particle with no electrical charge.

D any electrically charged particle.

5. The mystery element commonly combines with halogens. Which of the following elements is not a halogen?

A Iridium (Ir)

B Chlorine (CI)

C Iodine (I)

D Astatine (At)