Classification ...

The third period (n = 3) begins at sodium with addition of first electron to

Electronic configuration of an element is:

According to IUPAC nomenclature,element Ununnillium have an atomic number of:

Atomic number of element Unnilhexium is:

Choose one of the following in the order of increasing radii:

According to the recommendation of International Union of Pure and Applied Chemistry (IUPAC), the groups in the modern periodic table are numbered from

In the modern periodic table

It is now recognized that the ‘Modern Periodic Law’ is essentially the consequence of 

Mendeleev proposed that some of the elements were still undiscovered and, therefore, left several gaps in the table. He left the gap under aluminium and a gap under silicon, and called these elements Eka-Aluminium and Eka-Silicon. These were later discovered and named

Mendeleev relied on the similarities in the empirical formulas and properties of the compounds formed by the elements. He realized that some of the elements did not fit in with his scheme of classification if the order of atomic weight was strictly followed. He therefore