Henry Moseley was an English physicist who experimentally demonstrated that the major properties of an element are determined by the atomic number, not by the atomic weight, and established the relationship between atomic number and the charge of the atomic nucleus.
In 1914 Moseley published a paper in which he concluded that there were 3 unknown elements between Al and Au (there are, in fact, 4). He also concluded correctly that there were only 92 elements up to and including Uranium and 14 rare-earth elements.