Periodic table block

A block of the periodic table of elements is a set of adjacent groups. The term appears to have been first used (in French) by Charles Janet. [1] The respective highest-energy electrons in each element in a block belong to the same atomic orbital type. Each block is named after its characteristic orbital; thus, the blocks are:

* s-block
* p-block
* d-block
* f-block
* g-block (hypothetical)

The block names (s, p, d, f. and g) are derived from the quality of the spectroscopic lines of the associated atomic orbitals: sharp, principal, diffuse and fundamental, the rest being named in alphabetical order. Blocks are sometimes called families.

1. ^ Charles Janet, La classification helicoidal des elements chimiques, Beauvais, 1928