Jim Smith, age 14, of Charleston, UV, Va., for his question:
Who first figured out the theory of the atom?
The word atom means indivisible ‑ something which cannot be divided into anything smaller. True, the atom is composed of smaller particles and atoms can be smashed to bits. But, when this happens, the atom is no longer an atom. The world and everything in it is composed of atoms. They combine with each other, separate and re‑combine, to form and reform .the countless substances around us.
The idea that the world is built from atoms is not new. It occurred to the ancient Greeks, who seem to have thought of everything. To them, this idea explained the changing world. They thought of atoms as little bricks which built, tore down and rebuilt the world of matter.
The alchemist of the Dark Ages also thought that the world was built from a few basic ingredients. He thought there were four of them ‑ earth, air, fire and water. And he called them the elements. He also thought that if ho knew the right magic he could change, or transmute, one substance into another. Countless hours were wasted in an effort to change worthless lead into precious gold.
The modern atomic theory was born early in the 19th Century. It was new and original. But it did draw from the old idea of the atom as an indivisible building block. It did show that the old. Greeks had the right idea, though they had not the skills nor the equipment to develop it.
The 18th Century was bright with new scientific thought. One by one the old puzzles were being solved. While the great thinkers argued, a modest English schoolmaster was studying the weather and the atmosphere. He was John Dalton, color‑blind and a Quaker. In 1808 he published the atomic theory we now accept. His theory grew from his studies of the air.
Dalton based his theory on the indivisible atom. “Thou knowest,” he said in his quaint Quaker talk, “thou canst not cut an atom. Every element”, he stated, “is made of atoms of one sort. And all the atoms of a particular element have the same weight.” He found that there were a limited number of elements but the number was far greater than the four elements of the alchemist. In fact earth, air, fire and water were not basic elements at all.
The Quaker schoolmaster was able to explain how his basic elements made and remade the changing world. He stated that atoms combine in definite proportions to firm compounds. The atoms in each recipe must always be whole numbers for, thou canst not cut an atom.
Dalton worked out a system of symbols for his elements and compounds. Oxygen was a circle, hydrogen a circle with a dot in the center. Water was these two symbols joined with a line to show that it was a chemical compound. For Dalton saw the chemical nature of atoms and understood the chemical reactions between the elements.
Other chemists developed Dalton's work to completion. Letters and numbers replaced his strange symbols. The atomic weights which puzzled him. were worked out. Study of the chemical reaction of elements is still going on. Little, if any, of this work contradicts the atomic theory as set forth by John Dalton, Quaker schoolmaster.