Name that element! Which element on the periodic table helps brighten your smile, adds flavor to soda pop, and lights up your television? Follow these eight clues to find out. Then, turn the page to test your chemistry IQ.

DID YOU KNOW?

* Phosphorus is commonly found in fertilizers. And runoff of fertilizers from farms into rivers and lakes can cause harmful algal blooms. Algal blooms can decrease the amount of oxygen in a waterway, causing some marine life to suffocate.

CRITICAL THINKING:

* When excessive amounts of phosphorus leak into waterways, the effects on marine life could be deadly. What could be done to prevent this from happening?

CROSS-CURRICULAR CONNECTIONS:

MATH: A radioactive element is one with in unstable nucleus that decays over time. And half-life is the time it lakes for a radioactive substance to lose half its radioactivity. Phosphorus-32 (P-32) is a special radioactive form of phosphorus, and its half-life is approximately 14 days. Calculate how many days it would take for a 10-gram simple of P-32 to break down to 0.75 grams?

RESOURCES

* For more information about phosphorus, check out this Web page from the American Chemistry Council:

www.phosphatefacts.com/index.asp

* For information on calcium intake, read this fact sheet from the National Institute of Child Health and Human Development: www.nichd.nih.gov/milk/milk_facts.htm

CLUE 1

PRECIOUS ROCK

Like most elements, the mystery element is rarely found in its pure state in nature. Instead, this nonmetal combines with calcium (Ca) and fluorine (F) to form a mineral (naturally occurring solid with a uniform structure) called apatite. The mineral got its name, which means "deceit" in Greek, because its variety of crystal colors--from emerald green to pale pink--have fooled people into thinking that it's a precious gemstone.

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

CLUE 2

PRIME TIME

The mystery element lights up your television screen. When you switch on the TV, electrons stream through a tube at the rear of the television. These negatively charged particles hit the back of the TV screen and collide with a coating made of this element. The electrons give the element energy, which causes your TV to flouresce, or glow. Sulfur (S), an element in the same period, or row on the periodic table, as the mystery element is also used in flourescent materials.

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

CLUE 3

FIZZ FACTOR

Love the tangy taste of your favorite soda? To help flavor the drinks, manufacturers add the mystery element. In the soda, it's combined with hydrogen (H) and oxygen (O), forming an acid. Result? "[The mystery element] gives a tart or sour taste to soft drinks." says Nicole Bradley, a spokesperson at Pepsi. Besides adding flavor, the acid acts as a preservative, increasing the amount of time soda can stay on store shelves, says Bradley.

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

CLUE 4

BUILDING BONES

After calcium (Ca), the mystery element is the second most abundant element in your body, and most of it is found in your bones. [The mystery element] combines with calcium to form bones that are rigid and strong, says Curt Fischer, a biologist at Massachusetts Institute of Technology. To help keep bones healthy, Fischer recommends eating foods containing milk and whole wheat, which are loaded with the mystery element.

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

CLUE 5

BLOOM BOOSTER

Without the mystery element, sunflowers couldn't grow so lofty. That's because it makes up chloroplasts, or the tiny green structures where photosynthesis occurs. Inside these structures, the plant uses sunlight energy to make food and grow. To ensure healthy chloroplasts, farmers add the mystery element to soils as a fertilizer. These nutrient pellets also contain nitrogen (N), which is in the same group, or column on the periodic table, as this element.

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

CLUE 6

TWICE A DAY

The mystery element keeps your teeth clean and bright. It combines with calcium (Ca) to form an abrasive in toothpaste, which scrubs the surfaces of teeth. When you brush, this scrubber removes hard yellow plaque and food stains without damaging the enamel, or the shiny surface of your teeth. "After you brush, [the mystery element] that's in the toothpaste keeps your teeth feeling smooth and polished," says Tonia Elrod, a spokesperson at Crest.

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

CLUE 7

MAKE IT TOASTY 

This element gives matches the spark they need to start a marshmallow-roasting campfire. To be stable, the mystery element needs three additional electrons. So it binds with three of its own atoms to share their electrons. The resulting molecule, or particle of two or more atoms joined together, is used to coat match tips. When the coated match tip is struck against a rough surface, the bond between the atoms breaks and the now-unstable mystery element ignites. Hint: With three more electrons, this element has the same number of electrons as Argon (Ar).

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

CLUE 8

GAME OF LIFE

The mystery element is a major component of DNA, a chemical that carries hereditary information. Shaped like a twisted ladder, a DNA molecule contains "rungs" of nitrogen (N) bases that are held together by a combination of the mystery element and a sugar. "Without [the mystery element], you wouldn't have DNA, the basis for all life," says Fischer. Hint: This nonmetal has 15 protons in its nucleus, or center.

GAME'S OVER. NOW TURN TO PAGE 20.

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 and 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.

It's Your Choice Test your chemistry IQ! Answer the following questions about elements and the periodic table.

1. Name that element!

2. The mystery element combines with calcium (Ca) and to form apatite.

A Chlorine (CI)

B Gold (Au)

C Fluorine (F)

D Copper (Cu)

3. Which of the following is a member of group 2?

A Scandium (Sc)

B Silicon (Si)

C Aluminum (Al)

D Radium (Ra)

4. How many protons are in the nucleus of a nitrogen (N) atom?

A 1

B 4

C 7

D 52

5. Which of the following has the highest atomic number?

A Helium (He)

B Phosphorus (P)

C Oxygen (O)

D Boron (B)

6. Which of the following elements is a nonmetal?

A Bromine (Br)

B Titanium (Ti)

C Gallium (Ga)

D Potassium (K)

ANSWERS

1. Phosphorus 2. c 3. d 4. c 5. b 6. a

CHECK FOR UNDERSTANDING

DIRECTIONS: On a separate sheet 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. Phosphorous is commonly found in its pure state in nature.

2. Phosphorous is commonly added to fruit juices to give them an extra tangy flavor.

3. Phosphorus helps keep your teeth clean and bright.

ANSWERS

1. Dispute: Like most elements, phosphorous is rarely found in its pure state in nature. Instead, this nonmetal combines with calcium and fluorine to form a mineral called apatite.

2. Dispute: Phosphorous in commonly added to soda pop In the soda, it's combined with hydrogen and oxygen to form an acid, which helps gives a tart or sour taste to soft drinks. Besides adding flavor, the acid acts as a preservative, increasing the shelf life of soda.

3. Defend: Phosphorus combines with calcium to form an abrasive in toothpaste, which scrubs the surfaces of teeth.