Ensayo

3.1. The Periodic table

The periodic table is a tabular display of the chemical elements, organized on the basis of their atomic numbers and chemical properties.Elements are presented in increasing atomic number.

1789: Antoine Lavoisier published a list of 33 chemical elements. Although Lavoisier grouped the elementsinto gases, metals, nonmetals, and earths

1829: Johann Wolfgang Döbereiner observed that many of the elements could be grouped into triads (groups of three) based on theirchemical properties. Lithium, sodium, and potassium, for example, were grouped together as soft, reactive metals: Law of Triads

1843: German chemist LeopoldGmelin worked with this system; he had identified ten triads, three groups of four, and one group of five

1857:  Jean-Baptiste Dumas published a work describingrelationships between various groups of metals

1858: German chemist August Kekulé had observed that carbon has a tendency to bond with other elements in a ratio of one tofour. Methane, for example, has one carbon atom and four hydrogen atoms. This concept eventually became known as valency

1864, fellow German chemist Julius LotharMeyer published a table of the 49 known elements arranged by valency. The table revealed that elements with similar properties often shared the same valency

Englishchemist John Newlands produced a series of papers in 1864 and 1865 that described his own classification of the elements: He noted that when listed in order of increasingatomic weight, similar physical and chemical properties recurred at intervals of eight, which he likened to the octaves of music.

Mission: Draw the Periodic table