are there elements that are also missing?
There were seven elements  which were not found and therefore identified as still undiscovered, but from 1918 to 1947, all seven of these missing elements were discovered
Atomic number
After Moseley's death in 1915, the atomic numbers of all known elements from hydrogen to uranium ("Z" = 92) were examined by his method. There were seven elements (with "Z" < 92) which were not found and therefore identified as still undiscovered, corresponding to atomic numbers 43, 61, 72, 75, 85, 87 and 91. From 1918 to 1947, all seven of these missing elements were discovered. By this time, the first four transuranium elements had also been discovered, so that the periodic table was complete with no gaps as far as curium ("Z" = 96).
the density of osmium which is the densest metal It is approximately twice as dense as lead and slightly denser than iridium. what is osmium? It is a chemical element with the symbol Os and atomic number 76. where did it get its name from? From Greek word  "osme" meaning "smell". who was the first one to discover numbers for atoms? Henry Moseley
wiki:1630842
Atomic number [SEP] Missing elements
After Moseley's death in 1915, the atomic numbers of all known elements from hydrogen to uranium ("Z" = 92) were examined by his method. There were seven elements (with "Z" < 92) which were not found and therefore identified as still undiscovered, corresponding to atomic numbers 43, 61, 72, 75, 85, 87 and 91. From 1918 to 1947, all seven of these missing elements were discovered. By this time, the first four transuranium elements had also been discovered, so that the periodic table was complete with no gaps as far as curium ("Z" = 96).