Number of elements from the following that CANNOT form compounds with valencies which match with their…
Number of elements from the following that CANNOT form compounds with valencies which match with their respective group valencies is ______.
B, C, N, S, O, F, P, Al, Si
7
3
5
6
Solution
$\mathrm{N}, \mathrm{O}, \mathrm{F}$ can't extend their valencies upto their group number due to the non-availability of vacant $2 \mathrm{~d}$ like orbital.