Which of the following species represents an exception to the octet rule? PCI_3

Question

Which of the following species represents an exception to the octet rule? PCI_3 HBr CO_2 SiO_2 SF_4 Which of the following statement is true? The triple bond in N_2 has a larger bond order and a larger bond length than the single bond in F_2. The triple bond in N_2 and the single bond in F_2 have the same bond order and the same bond length. The triple bond in N_2 has a larger bond order and a smaller bond length than the single bond in F_2. The triple bond in N_2 has a smaller bond order and a smaller bond length than the single bond in F_2. The triple bond in N_2 has a smaller bond order and a larger bond length than the single bond in F_2.

Explanation / Answer

Q7

octet rule --> it must have, in total, 8 electrons...

so

PCl3 --> O has 3 bonds + 1 lone pair so = 3*2 + 2*1 = 6+2 = 8, this fulfils octet rule

HBr --> Bromine has 1 bond + 3 lone pairs so --> 1*2 +´3*2 = 2+6 = 8, this is octet

CO2 --> Carbon has 4 bonds, so 4*2 = 8, oxygen has 2 bonds + 2 lone pairs = 2*2 + 2*2 = 4+4 = 8, this is correct

SiO2 --> Silicon has 4 bonds = 4*2 = electorns, Oxygen has 2*2 + 2*2 = 4+ +4= 8

therefore

SF4 --> Sulfur has 1 lone pair + 4 bonds --> 1*2 + 4*2 = 2 + 8 = 10

this is an expanded octet, this is an excpetion!

SF4

Q8+

Bond order for N2 --> 3 (triple bond)

bond order for F2 --> 1 (single bond)

N2 = 110 ppm

and

F-F = 145

Clearly, N2 must have a smaller length, since it has stronger affinty toward each other

so..

choose

C

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