Question

how are blocks indicated?

Answer 1

A block of the periodic table is a set of chemical elements predominantly characterised by having their highest energy electrons in the same atomic orbital type. The term appears to have been first used by Charles Janet.[1] Each block is named after its characteristic orbital; thus, the blocks are:

s-block

p-block

d-block

f-block

The block names (s, p, d, f and g) are derived from the spectroscopic notation for the associated atomic orbitals: sharp, principal, diffuse, and fundamental.