From DNA to jet-propelled squid to proof that it's best to prepare dragon tonic using the metric system, David Schwartz's perennial science alphabet book entertains the science-curious and the science-phobic alike. By the time kids get to the end they'll agree-W is for Wow!

As a child, KIM DONER aspired to be a Ballerina-Veterinarian-Artist-- dancing at night, saving animals by day, and summering in Africa to draw wild animals from a treehouse. Today, she has made those dreams a reality-sharing her love of the arts through her award-winning children's books, rehabilitating wildlife, and planning a return to Africa with her husband. Kim lives in Tulsa, Oklahoma.


DAVID SCHWARTZ is the author of 50 children's books, including G IS FOR GOOGOL and Q IS FOR QUARK. He is a frequent guest speaker at schools in the US abroad. He lives with his wife-and co-author-YAEL SCHY in Oakland, California.


From the Hardcover edition.

A is for Atom

Suppose you took a cookie and cut it into little pieces, and then you cut those pieces into crumbs and those crumbs into littler and littler crumbs, and so on. Would you ever get to a point where it became impossible--no matter how good your knife, your hand, or your eyes--to cut any further? Would you ever reach the smallest possible piece of cookie? Or could you keep dividing it into smaller and smaller cookie bits...forever?

The ancient Greek philosophers wondered about things like this. One fellow, Democritus, said that all matter (that's what scientists call the "stuff" of the world) was made of tiny bits. He called these bits atoms, from the Greek word for "not cuttable." He believed the bits were put together in different ways to make different kinds of matter. Another philosopher, Aristotle, didn't think matter came in bits. He thought it all flowed together, like water running through your fingers.

Well, it turns out that Democritus was right. But it took many more centuries for scientists to prove the existence of atoms. They have since identified about 90 different kinds of atoms that occur naturally. Atoms are the building blocks of all matter. Matter can be made up of just one kind of atom, or different kinds of atoms joined together.

Atoms are tiny. A million atoms stacked on top of one another wouldn't be quite as thick as a hair on your head. About 100 billion of them would cover the period at the end of this sentence. An atom is so small that a single drop of water contains more than a million million billion atoms. That's 1,000,000,000,000,000,000,000! Of course their exact size depends on the atom. Some are smaller, some bigger. The smallest kind of atom is hydrogen, which also happens to be the most abundant atom in the universe. Uranium is the largest kind of atom, except for a few really big ones that scientists have made in laboratories.

Most of the time, atoms really are "not cuttable," as Democritus said. But scientists have special ways of breaking them apart in order to study them. (Please don't try this at home.) They have found that atoms themselves are made up of smaller parts.

Most of the space in an atom is a "cloud" of incredibly tiny electrons. Electrons whiz around at millions of miles per hour (and yet never get stopped for speeding). Because the electrons are going so fast, they're practically everywhere at once, and so scientists think of them as a cloud.

Somewhere deep inside the electron cloud is a nucleus. If the electron cloud were the size of a baseball stadium, the nucleus--floating somewhere in the middle of the stadium--would be smaller than the baseball. The nucleus of an atom is made from two types of particles--protonsandneutrons. They give the atom almost all of its mass (that's a measure of how much matter is in something--seeG is for Gravity).

Aside from mass, there's another big difference between an atom's electron cloud and its nucleus. The electrons have a negative electric charge, and the nucleus has a positive charge. Actually, it's the protons in the nucleus that are positively charged. As their name suggests, the neutrons are neutral (they have no charge). These positive and negative charges hold the atom together. This is because things with unlike charges are attracted to each other, while things with the same charge repel each other. (If you've ever played with magnets, you know that the negative and positive poles of two magnets are eager to know each other and you can tell because they stick together when they get close, but you can't force the two negative poles or the two positive poles to get personal.) An atom has an equal number of positive and negative charges, so it must have the same number of protons in its nucleus as electrons outside the nucleus.

The number of protons in the nucleus of an atom is called the at

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Excerpted from Q Is for Quark: A Science Alphabet Book by David Schwartz, David M. Schwartz
All rights reserved by the original copyright owners. Excerpts are provided for display purposes only and may not be reproduced, reprinted or distributed without the written permission of the publisher.