To which block do the elements with the following outer electronic configurations belong?
$(i)$ $6s^2 4f^3$
$(ii)$ $3s^2 3p^4$
$(iii)$ $3s^1$
$(iv)$ $3d^2 4s^2$

(N/A) $(i)$ $6s^2 4f^3$: The last electron enters the $4f$ orbital,so it belongs to the $f$-block.
$(ii)$ $3s^2 3p^4$: The last electron enters the $3p$ orbital,so it belongs to the $p$-block.
$(iii)$ $3s^1$: The last electron enters the $3s$ orbital,so it belongs to the $s$-block.
$(iv)$ $3d^2 4s^2$: The last electron enters the $3d$ orbital,so it belongs to the $d$-block.