2023 Chemical Bonding and Molecular StructureOctet Rule and Its Exceptions Medium Question 14 of 108 in Chemical Bonding and Molecular Structure

Amongst the following, the total number of species NOT having eight electrons around central atom in its outer most shell, is: $NH_3$, $AlCl_3$, $BeCl_2$, $CCl_4$, $PCl_5$

A 1
B 3
C 2
D 4

The answer is B.

Solution

$AlCl_3$, $BeCl_2$ and $PCl_5$ do not obey the octet rule.

$AlCl_3$, $BeCl_2$ and $PCl_5$ do not obey the octet rule. $AlCl_3$ and $BeCl_2$ are electron-deficient species (fewer than eight electrons in the valence shell of the central atom), whereas $PCl_5$ has ten electrons in the valence shell of phosphorus. The structures are: [add image]

Concept electron-deficient and expanded octet species

Chemical Bonding and Molecular Structure in past papers

108 questions from this chapter have appeared across 27 exam years.