Which and how many blocks are present in the periodic table? Explain the factors upon which this classification depends.

(N/A) There are four blocks present in the periodic table,which are $s$,$p$,$d$,and $f$ blocks.
This classification depends upon the atomic orbital into which the last electron enters in the ground state of the atom.
$1$. $s$-block: The last electron enters the $s$-orbital.
$2$. $p$-block: The last electron enters the $p$-orbital.
$3$. $d$-block: The last electron enters the $d$-orbital.
$4$. $f$-block: The last electron enters the $f$-orbital.