Using his table, Mendeleev was able to successfully predict the properties of three elements that had not yet been discovered. The final modern periodic table arrangement was finally proposed by Moseley in 1913 by ordering elements by their atomic number instead of their mass.
Similarly, how has the periodic table changed since 1869?
It's still changing today. The first periodic table in the "rows and columns" form we see today was invented by Dmitri Mendeleev in 1869. The periodic table has long-since filled in Mendeleev's gaps and has added new elements. It has even changed the weights of other elements.
Is the periodic table that we have today complete?
After scientists recently discovered four new elements, some experts have said the periodic table is now complete. Today, however, elements are measured by their atomic number, which is the number of protons in the nucleus.
How old is the periodic table?
In 1869, just five years after John Newlands put forward his law of octaves, a Russian chemist called Dmitri Mendeleev published a periodic table. Mendeleev also arranged the elements known at the time in order of relative atomic mass, but he did some other things that made his table much more successful.