Man-made elements, also known as synthetic elements, have been made artificially as isotopes from other elements. The first was technetium (atomic number 43). Some of these elements do show up in nature in minuscule amounts, emerging as a byproduct of radioactive decay.
Promethium (atomic number 61), astatine (85), francium (87) and the transuranium elements (93 and everything higher) are the other man-made elements. All of the man-made elements through fermium (100) came about when scientists used alpha particles or neutrons to hit a heavy element such as plutonium or uranium. For elements 101 and higher, scientists fuse the nuclei of two of the lighter elements, as with the blending of carbon and californium.
Making elements with atomic numbers over 100 is extremely difficult as they can only be made an atom at a time, and their extremely short half-lives, milliseconds in some cases, require identification through methods beyond the traditional chemical separations. As of 2015, one man-made element that remains elusive is the isotope of element 114 with 184 neutrons. Because its nucleus would contain a full set of protons and neutrons, some scientists believe it would not decay quickly and instead would have a half-life that lasted for years. However, no isotopes of element 114 have yet been made with 184 neutrons.