There are many more elements than just 91. There are in fact 114 officially recognised elements. All these elements are arranged on the Periodic Table of the Elements.
Elements with atomic numbers 90 to 103 are known as actinides.
There were 103 elements on the periodic table in 1968.
58 through 71 are lanthanides, 90 through 103 are actinides.
The elements with atomic numbers 58-71 are called lanthanides, and those with atomic numbers 90-103 are called actinides. These elements are part of the inner transition metals and have unique properties due to their electron configurations.
There are 102 elements named in the song lyrics, in a totally disorderly order. The date of the song (1960-ish) gives a clue to which elements. For a long time around then there were just 102 recognised elements, all atomic numbers up to 102, and 103 and beyond were in process of discovery and recognition. So the elements that were not included were those artificial elements that had not yet been recognised: elements 103-114 and 116.
103
Elements with atomic numbers 90 to 103 are known as actinides.
There were 103 elements on the periodic table in 1968.
58 through 71 are lanthanides, 90 through 103 are actinides.
193
Elements 89 (Actinium) through 103 (Lawrencium) on the periodic table of elements.
curium
14
The Actinides.
Actinides family, atomic number 103.
Actidines.
The elements with atomic numbers from 90 to 103 are called actinides. These elements are known for being radioactive and having partially filled 5f orbital. They include well-known elements like uranium, plutonium, and americium.