In 1902, Bohuslav Brauner suggested there was an element with properties intermediate between those of the known elements neodymium (60) and samarium (62); this was confirmed in 1914 by Henry Moseley who, having measured the atomic numbers of all the elements then known, found there was no element with atomic number 61.
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In 1902, Czech chemist Bohuslav Brauner found out that the difference between neodymium and samarium is the largest of all neighboring lanthanides pairs; as a conclusion, he suggested there was an element with intermediate properties between them.