of , , , and elements, respectively. The seventh period is incomplete and like the sixth period would have a theoretical maximum (on the basis of quantum numbers) of elements. In this form of the Periodic Table, elements of both sixth and seventh periods (lanthanoids and actinoids, respectively) are placed in separate panels at the bottom * . .
NOMENCLATURE OF ELEMENTS WITH ATOMIC NUMBERS > The naming of the new elements had been traditionally the privilege of the discoverer (or discoverers) and the suggested name was ratified by the IUPAC. In recent years this has led to some controversy. The new elements with very high atomic numbers are so unstable that only minute quantities, sometimes only * Glenn T. Seaborg’s work in the middle of the th century starting with the discovery of plutonium in , followed by those of all the transuranium elements from to led to reconfiguration of the periodic table placing the actinoids below the lanthanoids.
In , Seaborg was awarded the Nobel Prize in chemistry for his work. Element has been named Seaborgium (Sg) in his honour. Fig. .
Long form of the Periodic Table of the Elements with their atomic numbers and ground state outer electronic configurations. The groups are numbered - in accordance with the IUPAC recommendations. This notation replaces the old numbering scheme of IA–VIIA, VIII, IB–VIIB and for the elements. III A IV A V A VI A VII A ← VIII → I B II B IA IIA III B IV B V B VI B VII B a few atoms of them are obtained.
Their synthesis and characterisation, therefore, require highly sophisticated costly equipment and laboratory. Such work is carried out with competitive spirit only in some laboratories in the world. Scientists, before collecting the reliable data on the new element, at times get tempted to claim for its discovery. For example, both American and Soviet scientists claimed credit for discovering element .
The Americans named it Rutherfordium whereas Soviets named it Kurchatovium. To avoid