Major groups of elements

A cornerstone of modern chemistry is the arrangement of elements into groups with similar chemical properties. Scientists of the 1700’s and 1800’s collected facts about the elements then known. Soon, similarities among some of these elements were recognized. By the second half of the 1800’s, scientists had enough information to begin classifying all the elements.

, Avogadro’s hypothesis had paved the way for determining relative atomic weights, making it possible to classify all the known elements according to their properties and to list them by weight, from lightest to heaviest. Dmitri Mendeleev, a Russian chemist, began this classification in 1869. By arranging the elements in columns, the forerunner of today’s periodic table, Mendeleev discovered the natural order that exists among elements. Listing the 57 known to him, Mendeleev noticed that certain chemical properties reappeared in every eighth element. This repetition at regular intervals came to be known as the periodic law.

Mendeleev’s table not only listed the elements known in his time—it also left gaps where the periodic law predicted that elements of a certain weight with known properties would appear. He predicted the properties of three such unknown elements. Toward the end of the century, when the “missing” elements—gallium, scandium, and germanium— were discovered, scientists had all the proof they needed of the validity of Mendeleev’s grand concept.

Read More Major groups of elements