Question

Which one of the following compounds does not exist ?

• A. $NCI_5$
• B. $AsF_5$
• C. $4SbCl_5$
• D. $PF_5$

Answer 1

Answer: (A)

$NCI_5$

Answer 2

$NCl_5$ does not exist as N cannot have a covalency of 5. This is because N can not expand its octet due to non-availability of $d$-subhell in the valence shell.