Question

The molecule in which an atom is associated with more than $8{e^ - }$ is known as a hyper-valent molecule. All hyper-valent molecules must have $d\pi - p\pi$ bonding but the molecule having back bonding need not always have $d\pi - p\pi$ bonding. Which of the molecules is not hyper-valent but completes its octet.
A.$AlC{l_3}$
B.$AlB{r_3}$
C.$Al{F_3}$
D.$B{F_3}$

Answer 1

We have to know that hyper-valent particles are one of the exemptions for the octet rule. Holding in most hyper-valent particles is very much supported by the Rundle–Pimentel model (three-focus four-electron bond), and high ionic holding between the ligands and the focal iota is fundamental for balancing out hyper-valent atoms.

Complete answer:
We have to know that, $AlC{l_3}$ is still electron inadequate. The aluminum has just six electrons in its valence shell. Estimates show that the equation of the fume is $A{l_2}C{l_6}$ . It exists as a dimer (two atoms consolidated) in which two electrons from one chlorine are imparted to the aluminum of the other $AlC{l_3}$ particle to shape a facilitated bond.
We have to know that, aluminum bromide $AlB{r_3}$ is an ionic compound that is framed from the response of aluminum with fluid bromine. Aluminum particles surrender three electrons bringing about $A{l^{3 + }}$ and bromine molecules acquire one electron each subsequent in $B{r^ - }$ .
We have to know that, $Al{F_3}$ . Since, because of exceptionally high electronegativity of fluorine atoms $Al{F_3}$ is ionic in nature. Furthermore, $A{l^{3 + }}$ particle has eight electrons in the valence shell. So, $Al{F_3}$ isn't hypo-valent. These total their octet due to back holding with the solitary pair on the halogen. $Al{F_3}$ , it is an ionic compound which comprises $A{l^{3 + }}$ and $3{F^ - }$ .
We have to know that, $B{F_3}$ is a particle consisting of a $s{p^2}$ mixture of Boron covalently reinforced with three molecules of fluorine. The covalent bond discloses to us that electrons are shared, as opposed to lost by boron, and acquired by fluorine.

Therefore, the correct option is (C) $Al{F_3}$.

Note:
As we know that hyper-valent compounds are normal and overall are no less steady than intensifiers that adjust to the octet rule. It is accordingly, contended that iotas of this and resulting periods can use the unfilled d orbitals to oblige electrons past an octet and subsequently grant the development of hyper-valent species.