Question

Give the general electronic configuration of lanthanides and actinides?

Answer 1

A block of the periodic table is a group of elements linked together by the orbitals in which their valence electrons or vacancies are located. The $s$ block, $p$ block, $d$ block, and $f$ block are all named after their respective orbitals.

Complete answer:
The elements of the $f$ block are divided into two groups: lanthanoids and actinoids. These elements are known as inner transition metals because they provide a transition between the $s$ and $d$ blocks of the periodic table in the ${6^{th}}$ and ${7^{th}}$ rows.
$f$ block elements have electrons attached to the $f$ sub-orbitals of the $\left( {n - 2} \right)$ level, electrons are located between $\left( {n - 1} \right)d$ and $ns$ block elements in the periodic table, and their properties are identical to those of $d$ block elements.
From lanthanum to lutetium, the lanthanide or lanthanoid sequence of chemical elements consists of $15$ metallic chemical elements with atomic numbers $57 - 71$ . Rare-earth elements are a group of elements that includes these and the chemically related elements scandium and yttrium.
Actinium through lawrencium is the $15$ metallic chemical elements in the actinide sequence, with atomic numbers ranging from $89 - 103$ . The first element in the sequence, actinium, gives the actinide series its name. In general discussions of actinide chemistry, the informal chemical symbol $An$ is used to refer to any actinoid.
The general electronic configuration is given as,
Lanthanides : $\left[ {Xe} \right]4{f^{1 - 14}}5{d^{0 - 1}}6{s^2}$
Actinides : $\left[ {Rn} \right]5{f^{0 - 14}}6{d^{0 - 2}}7{s^2}$

Additional Information:
Except for promethium, all lanthanides are non-radioactive, whereas all actinide sequence elements are radioactive.
While lanthanides do not appear to form oxo-cations, the actinide sequence has many oxo-cations. The compounds formed by lanthanides are less basic than those formed by actinides, which are extremely basic.

Note:
The elements of the $f$ block are mentioned separately at the bottom of the periodic table. They are a combination of the ${6^{th}}$ and ${7^{th}}$ periods.