Halogen octet rule followed

Most of the common elements in organic compounds—C, N, O, and the halogens— follow the octet rule. Hydrogen is a notable exception, because it accommodates only two electrons in bonding. Additional exceptions include boron and beryllium (second-row elements in groups 3A and 2A, respectively), and elements in the third row (particularly phosphorus and sulfur). 

There are only four electrons around beryllium and six around boron. Why don t lone pairs from the surrounding halogen atoms form multiple bonds to the central atoms, thereby satisfying the octet rule Halogens are much more electronegative than beryllium or boron, and formal charges show that the following are unlikely structures ... 

The number of covalent bonds formed by an atom is termed its COVALENCY. The covalency of an atom is equal to the number of electrons the atom needs to become isoelectronic with a noble gas. Some of the more common elements have the following covalencies when they follow the octet rule and also have no charge hydrogen and the halogens, 1 oxygen and sulfur, 2 nitrogen and phosphorus, 3 carbon and silicon, 4. LEWIS ELECTRONIC FORMULAS, in which bonds and unshared electrons are shown, are given for a few typical compounds of these elements ... 

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