Mendeleev insisted that the periodic table was primarily a classification ... from the possible combinations of the three spatial quantum numbers as well as Pauli's fourth quantum number ...

The periodic table, also known as the periodic table of (the) chemical elements, is a tabular display of the chemical elements. It is widely used in chemistry, physics, and other sciences, and is ...

National Periodic Table Day, observed annually on February 7, honors one of the most significant achievements in scientific ...

but there were always a few missing blocks in the periodic table. These elements, with atomic numbers of 113, 115, 117, and 118 comprise the missing parts of period 7 – the lowest row – of the ...