WHICH OF THE FOLLOWING SPECIES DOES NOT OBEY OCTET RULE?
1) SiF4
2) PCI5
3) ICL
4) BF- 4
The correct option is (2).
To find the species which does not obey the octet rule is calculated by calculating the total number of electrons in the species. Total number of electrons is calculated by the number of bonded electrons + number of electrons in lone pairs
(1) SiF4 = Four bond pairs, no lone pair. It means it has total of 8 electrons.
(2) PCl5 = Five bond pairs, no lone pair. It means it has total of 10 electrons
(3) ICl = One bond pair, 3 lone pairs. It means it has total of 8 electrons.
(4) BF4- = Four bond pairs no lone pairs. It means it has total of 8 electrons.
Species having electrons less than 8 or more than 8 will not obey the octet rule. So, PCl5 which has 10 electrons is the correct option.
To find the species which does not obey the octet rule is calculated by calculating the total number of electrons in the species. Total number of electrons is calculated by the number of bonded electrons + number of electrons in lone pairs
(1) SiF4 = Four bond pairs, no lone pair. It means it has total of 8 electrons.
(2) PCl5 = Five bond pairs, no lone pair. It means it has total of 10 electrons
(3) ICl = One bond pair, 3 lone pairs. It means it has total of 8 electrons.
(4) BF4- = Four bond pairs no lone pairs. It means it has total of 8 electrons.
Species having electrons less than 8 or more than 8 will not obey the octet rule. So, PCl5 which has 10 electrons is the correct option.