Paula Belk, age 8, of Monroe, North Carolina, for her question:

What exactly is silver?

The scientists say that silver is a chemical element. This means that it is made from atoms that are all alike. There is no difference between one silver atom and the next. Naturally an atom of silver is much, very much, too small for human eyes to see. In fact, even the strongest microscope invented can only show the dim shadow of a silver atom. There are zillions, zillions and zillions of these tiny atoms in the smallest silver coin.

Because all silver atoms are all alike, they can build only one kind of material. And we know what this beautiful material looks like. It is a gentle gray metal and we can polish it to shine like a moonbeam. We treasure silver, the chemical element, because it is beautiful and useful. But mostly because it is hard to come by. The earth has plenty of nickel and lots of silvery gray aluminum     but only a very little silver. This is why silver costs more than nickel or aluminum.