Name that element! Which element on the periodic table is a nightmare for bugs, helps keep your refrigerator cold, and protects your computer's hard drive? Follow these eight clues to find out. Then turn the page to test your chemistry IQ

CLUE 1

BUDDY SYSTEM

In its pure form, the mystery element looks greenish-yellow. But this highly reactive nonmetal easily combines with other elements to form compounds. The mystery element beats all other elements in the number of different elements it'll team up with, says Darryl DesMarteau, a chemistry professor at Clemson University. "It reacts to form compounds with all other elements except helium, neon, and argon."

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

CLUE 2

BUGS BEWARE

Our bodies contain small amounts of compounds of the mystery element, but larger amounts are deadly. People have learned to use that toxicity to fight an enemy: cockroaches. Compounds of this element are found in powdered insecticides. Cockroaches walk through the powder, which sticks to them. They use their mouths to clean off the irritating powder, ingesting the poison. Days later, the roaches go belly up.

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

CLUE 3

IT'S A BLAST

Volcanic gases include a compound of the mystery element. During an eruption, this compound can stick to ash particles. Cattle grazing on ash-covered grass may eventually go lame as an overdose of the mystery element damages their bones. Ironically, smaller amounts of this element strengthen bones.

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

CLUE 4

HIGH-TECH

Inside your computer's hard drive, read/write heads transfer data onto and off spinning disks. To keep the heads from wearing out the disks, manufacturers coat the disks with a lubricant containing the mystery element. For many high-tech applications, "You can probably find some [of the mystery element] in it," says DesMarteau. (Hint: This lubricant also contains oxygen, which, like the mystery element, is a gas in its natural state.)

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

CLUE 5

COOL COMBO

A once-popular refrigerant contains this element and chlorine. Although the refrigerant successfully chilled things, it had a not-so-cool effect: The refrigerant's chlorine damaged Earth's ozone layer. To keep this protective gas in the upper atmosphere intact, refrigerants now contain the mystery element-minus the chlorine.

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

CLUE 6

NON-STICK

Teflon [R] pans owe their nonstick reputation to this element. "Teflon [R] is nothing more than a carbon backbone that's got [the mystery element] bonded to it," explains Jean'ne Shreeve, a chemistry professor at the University of Idaho. This bond is so strong that the mystery element's atoms form a shield over the carbon atoms. This shield repels other substances. (Hint: The mystery element and carbon are in the same period, or row.)

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

CLUE 7

DRY UP

Heating and stretching Teflon (R) yields Gore-Tex (R). This waterproof material is full of microscopic pores. These pores are 700 times larger than a single water molecule, yet 20,000 times smaller than a water drop--consisting of many molecules. When you wear GoreTex [R], raindrops and snow can't get in. But sweat vapor--which exists as single molecules--can escape. Either way, you stay dry.

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

CLUE 8

SAY CHEESE

When microbes break down food, they release acids. To protect your pearly whites, a small amount of a compound of the mystery element is added to toothpaste and drinking water. The element, which has nine protons, strengthens the compounds in your tooth enamel. This makes the coating much more resistant to chemical attack, says DesMarteau.

GAME'S OVER. NOW TURN TO PAGE 22.

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.

The Periodic Table

The periodic table is a systematic way to organize Earth's elements, substances that consist of atoms of only one kind. Today, there are 112 known and named chemical elements. Elements are arranged according to their increasing atomic numbers. Hydrogen (H), for example, has an atomic number of 1 and is the lightest known natural element on Earth. Scientists have created elements with atomic numbers greater than 92, but they don't exist naturally. Some scientists think they may have created elements heavier than 112, but until an element is confirmed by two different labs, it usually isn't listed on the periodic table.