Who invented the periodic table?
Who invented the periodic table? Dmitri Mendeleev, a Russian chemist, is credited as the inventor of the periodic table and is often called its father: he invented the arrangement, created and published his first version in 1869 and arranged the 63 known elements by atomic weight and chemical properties, leaving gaps for elements not yet discovered.
His predictions for these missing elements, which he called eka-aluminium, eka-boron and eka-silicon, proved right when gallium (1875), scandium (1879) and germanium (1886) were found, and that success made his table the accepted version. Others contributed: Johann Döbereiner noticed triads of similar elements in 1829, Alexandre-Émile Béguyer de Chancourtois and John Newlands proposed periodic arrangements in the 1860s, and Julius Lothar Meyer, a German chemist, developed a similar table independently around 1864 and 1870. Readers also ask “what is a period on the periodic table”, which has its own short answer.
Henry Moseley later showed in 1913 that elements should be ordered by atomic number rather than atomic weight, giving the modern periodic table its form. Mendeleev's key idea was to put elements with similar properties in the same column even if that meant leaving a gap, and he predicted the properties of eka-silicon (germanium), such as an atomic weight near 72 and a density near 5.5 g/cm3, very close to what Clemens Winkler found in 1886. Another common question on this site is “what is the atomic number of an element”.
Not every placement fitted: his order by atomic weight was changed to put tellurium before iodine, even though tellurium is heavier, because their chemical properties demanded it, and later work showed that the atomic number, not the weight, is what matters. The noble gases discovered by William Ramsay and Lord Rayleigh in the 1890s fitted in as a new group, and Moseley's work in 1913 removed the remaining ordering problems. Readers also ask “what are the 5 elements”, which has its own short answer.
The modern table is still called Mendeleev's table in many countries, and element 101, mendelevium, is named after him. He is remembered not for being first, but for using the pattern to make predictions that could be tested. Glenn Seaborg's actinide concept in the 1940s placed the actinides in their own row below the main body.