![]() ![]() An element's period number is the highest unexcited energy level for an electron of that element. The rows of the periodic table are called periods.At the time of this writing, the most recent version of the periodic table was approved in December 2018. The International Union of Pure Applied Chemistry, IUPAC, revises the periodic table as new data becomes available.It is the lightest element that has only radioactive isotopes (none are stable). Technetium was the first element to be made artificially.Some sources state more elements occur naturally because heavy elements may transition between elements as they undergo radioactive decay. All of the other elements are strictly human-made. ![]() ![]() There are about 94 elements on the periodic table that occur in nature.It wasn't the first table that organized the elements according to periodic properties. Although Dmitri Mendeleev is most often cited as the inventor of the modern periodic table, his table was just the first to gain scientific credibility. ![]()
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