In $f$-block elements, orbitals are progressively filled by the electrons.
In $f$-block elements, orbitals are progressively filled by the electrons.
$3 f$ and $4 f$
$4 f$ and $5 f$
$5 f$ and $6 f$
$6 f$ and $7 f$
Solution
The general electronic configuration of $f$-block elements is
$(n-2) f^{(0-14)}(n-1) d^{(0-1)} n s^2$
General electronic configuration of
lanthanoids is [Xe] $4 f^{1-14} 5 d^{0-1} 6 s^2$
and actinoides is $[\mathrm{Rn}] 5 f^{1-14} 6 d^{0-1} 7 s^2$
So, $4 f$ and $5 f$ orbitals are filled in $f$-block elements.