Question

The octet rule is not followed by:
 A. ${F_2}$
 B. $NaF$
 C. $Ca{F_2}$
 D. $B{F_3}$

Answer 1

Hint: In order to find the solution, at first we have to check whether the given compounds satisfied octet rule or not and according to Octet Rule, each atom of an element should contain 8electrons in their valence shell, and also the electronic configuration should be same as a Noble Gas.

Complete step by step solution:
$B{F_3}$ does not follow the octet rule because in $B{F_3}$, $F$ element completes its octet by sharing one electron from ‘Boron’ whereas ‘Boron’ shares three electrons from three $F$ atom and has only 6 electrons in their outermost shell because it makes only three covalent bonds. Thus it has an incomplete octet. Boron has less than 4 outer electrons. Whereas according to the octet rule, each atom has 8 electrons in its valence shell and has the same electronic configuration as a noble gas.
Whereas, ${F_2}$ completes the octet rule because ${F_2}$ contains a single pair of electrons. Each Fluorine atom also has three pairs of electrons that are not shared further with any atom. It is combined with two electrons in the covalent bond.
And, $NaF$ also completes the octet rule because it is an ionic compound, formed by the complete transfer of electrons from a metal to a non-metal and the resulting ions have achieved an octet.
$Ca{F_2}$, in the formation of this compound, again the resulting ion satisfied an octet because two fluorine atoms and one calcium satisfy the rule. So, only $B{F_3}$ cannot achieve the octet rule.

Hence, the correct option is (D).

Note: The Octet Rule is violated in scenarios such that when there are an odd number of valence electrons, when there are too few valence electrons and last when there are too many valence electrons.