Michael Preisler, age 13, of Port Washington, Wisconsin, for his question:

Which is the earth's most plentiful element?

In its solid form, the most plentiful element is a pale blue crystalline substance. The temperature of the handsome solid is minus 218.4 degrees Centigrade and the merest touch produces frostbite. Fortunately, nature never presents the abundant element to us in this chilly state.

An element, as every science student knows, is made from atoms of one kind. And no more than approximately 100 different elements are used to make all the solids, liquids and gases of our teeming planet. The vast variety of substances are made, unmade and remade.by chemical combinations of the basic atoms in molecules. And molecules mingle to form assorted mixtures. Some of the basic elements are so rare that the earth cannot supply enough of their atoms to fill a thimble. A score of them are so plentiful that their atoms are the main ingredients in almost everything.

Suppose we could put each of the world's elements into a separate pile. One pile would be almost as big as all the others put together. This pile is.oxygen; by far the most plentiful element of our planet. There is a reason, however, why we could not cope with the world's supply in one pile. At normal earth temperatures, when oxygen is separated from other elements its atoms become separate gaseous particles and zoom off to merge with the other invisible gases of the air.

However, every day we stand and walk on the most plentiful element. We drink it, we wash ourselves and brush our teeth with it. We breathe it into our lungs and airplanes fly in it. A supply of oxygen atoms is gaseous at normal temperatures. At minus 183 degree# Centigrade the element becomes a pale watery blue liquid. It refuses to become solid until the temperature is chilled to minus 218.4 degrees. Yet at normal temperatures we have teeming oxygen atoms in a countless variety of solids, liquids and gases.

Oxygen atoms combine with atoms of silica, aluminum and scores of other elements to fort molecules. Molecules of compounds do not resemble their element ingredients. The molecules of almost all minerals contain oxygen atoms and, altogether, about 4 per cent of the earth's crest is composed of the earth's most plentiful element.

Every basic particle of water is a package of two small atoms of hydrogen arid one heavier atom of oxygen.. There are 1,720 pounds of oxygen in every ton of water. This ratio is in all the actual water of the seas and rivers, the clouds and the water vapor of the atmosphere. Free oxygen also makes up one fifth of the atmosphere's airy gases, And the world's most plentiful element is present : _ most of the complex chemicals of the human body. If you weigh 100 pounds, about 65 pounds of your total weight is oxygen, either in free atc:ns on ccmbir.e. i in molecules with other elements.

Oxygen alone is a colorless, odorless, tasteless gas. It happens to be one of the busiest and most chemically active of all the elements. It causes rust and other forms of oxidation, and various other forms of combustion. It supports life and both the plant and animal kinL3omr would soon perish without it, Its atoms eagerly combine chemically with other elements to form a countless assortment of solids, liquids and gases. Oxygen can form compounds with all other atoms except neon and a few of the inert gases.