In the 1860s, a Russian scientist named Dmitri Mendeleev was tying to come up with a logical way to arrange the elements. He noticed that in his arrangement, the elements in the same column had something in common with one another. What Mendeleev had developed is known as the periodic tale of the elements. Moseley help Mendeleev solving his arrangement problem. Moseley arranged the elements according to their atomic numbers insted of atomic masses.
More elemnts have been dscovered since Mendeleev's time. A modern periodic table contains 113 elements organized into eighteen groups and seven periods. The periodic table can be divided in ways other than into groups and periods. For example, the elements can be divided into metals and nonmetals and semiconductors. Another way to divide the periodictable is into natural and artificial elements. Artificial elements have a number of uses. Articficial element, americium(Am) is used in home smoke detector. ( )