Question

For which of the following compounds a valid Lewis structure cannot be drawn without violating the octet rule?

• A. $P{O}_4^{3-}$
• B. $Si{F}_4$
• C. $C{F}_4$
• D. $Se{F}_4$

Answer 1

Answer: (A), (D)

$Se{F}_4$

The Lewis structure of $P{O}_4^{3-}$ is:

The central atom $\left(P\right)$ has 10 valence electrons.

The Lewis structure of $Si{F}_4$ is:
The central atom $\left(Si\right)$ has 8 valence electrons.

The Lewis structure of $C{F}_4$ is:
The central atom $\left(C\right)$ has 8 valence electrons.

The Lewis structure of $Se{F}_4$ is:
The central atom $\left(Se\right)$ has 10 valence electrons.

Hence, $P{O}_4^{3-}$ and $Se{F}_4$ violate the octet rule.