Donald Meitze, age 12, of Old Bridge, N.J., for his question:
What exactly is an element?
The alchemists of the Middle Ages wore magicians gowns and talked of elements. They talked of four elements earth, air, fire and water. We may speak of the weather elements, such as winds and stormy rains. Modern scientists speak of 103 elements. But neither the weather elements nor the four elements of the ancients are on this list.
All the solids, liquids and gases in the world are made of atoms. A substance made of atoms of one sort is an element. In nature, there are only some 90 different elements. Sodium and chlorine are elements, so are oxygen and hydrogen. Most of the substances around us are compounds made of molecules of assorted atoms. Ordinary salt is a compound of the elements sodium and chlorine. Water is a composed of hydrogen and oxygen.
Several more elements have been made or found in addition to the common elements found in nature. The list now stands at 103 and still more elements will be added. All of them are charted on the Periodic Table of chemical elements, each in his own square. For the atoms of each element have qualities which make them different from all other atoms.
Every atom, however, has a nucleus charged with positive electricity. Every atom is orbited by at least one negatively charged electron. The number of its electrons equals the number of proton particles in its nueleus. The sma3lest atom is hydrogen, with one proton and one electron. A few hydrogen atoms and all other atoms have one or more neutral neutrons also in the nucleus.
The nature of an element depends upon its atomic number. This is the number of protons in the nucleus of its atom, which is the same as its orbiting electrons. The atomic number of hydrogen is one; of helium, it is two. An atom of hydrogen can gain a neutron without changing its nature. But if it gains a proton, it is an atom of hydrogen. The atomic numbers of the elements go in whole numbers from one to 103. The atomic weight of an element is the sum of alb. Its particles. The weight is not always a whole number.
The nature of an element depends upon its atomic number. Its chemical. Behavior depends upon the number of its orbiting electrons. When there is a similar ratio of the electrons, a number of elements form a family and share similar qualities. The metallic elements copper, silver and gold each have an outer shell of one electron. The gaseous elements neon, argon and krypton each have an outer shell of eight electrons. These and other fascinating items can be discovered by studying the Periodic Table of Chemical. Elements.