Synthetic Elements On Periodic Table. Synthetic elements , in chemistry, radioactive elements that were not discovered occurring in nature but as artificially produced isotopes. Those that are only very rarely made in nature and have sufficiently short lifetimes to not be observed in nature in anything but very small quantities.
In 1937, it became the first element to be discovered by synthesis in a laboratory — paving the way to the atomic age. Back in the year 1800, only 30 elements were known. When mendeleev proposed his periodic table in 1869, element 43 was unknown.