Periodic table

This representation of the periodic table shows the rare earth elements in the same rows as the elements that follow them.

The Russian chemist Dmitri Mendeleev is credited with recording the first periodic table, to understand the relationship between the known chemical elements.

Mendeleev's table organized the elements by their properties, and their atomic weight. It is called the periodic table because chemical properties recurred, periodically. Mendeleev lined up elements so elements that shared properties were listed below the lighter elements with those properties. Helium, the noble gas, lead the column that included the other noble gases, Neon, Argon, Krypton, and Xenon. Mendeleev's table had gaps in it, which he predicted showed the position of chemical elements that had yet to be discovered.