First systemization attempts

In 1789, Antoine Lavoisier published a list of 33 chemical elements, grouping them into gases, metals, nonmetals, and earths.

Chemists spent the following century searching for a more precise classification scheme. In 1829, Johann Wolfgang Döbereiner observed that many of the elements could be grouped into triads based on their chemical properties. Lithium, sodium, and potassium, for example, were grouped together in a triad as soft. German chemist Leopold Gmelin worked with this system, and by 1843 he had identified ten triads, three groups of four, and one group of five. Jean-Baptiste Dumas published work in 1857 describing relationships between various groups of metals. Although various chemists were able to identify relationships between small groups of elements, they had yet to build one scheme that encompassed them all.

In 1858, German chemist August Kekulé observed that carbon often has four other atoms bonded to it. Methane, for example, has one carbon atom and four hydrogen atoms. This concept eventually became known as valency; different elements bond with different numbers of atoms. In 1864, fellow German chemist Julius Lothar Meyer published a table with 44 elements arranged by valency. The table showed that elements with similar properties often shared the same valency.

English chemist John Newlands produced a series of papers in 1864 and 1865 noting that when the elements were listed in order of increasing atomic weight, similar physical and chemical properties recurred at intervals of eight; he likened such periodicity to the octaves of music. This Law of Octaves, however, was ridiculed by Newlands' contemporaries, and the Chemical Society refused to publish his work.Newlands was nonetheless able to draft a table of the elements and used it to predict the existence of missing elements, such as germanium. The