The third violation to the octet rule is found in those compounds with more than eight electrons assigned to their valence shell. The Octet Rule. If possible, apply the octet rule to your structure. These are called expanded valence shell molecules.Such compounds are formed only by central atoms in the third row of the periodic table or beyond that have empty d orbitals in their valence shells that can participate in covalent bonding. So we must move a lone pair in one of the oxygen bonds, back to the oxygen: This is possible due to availability of 3 d orbitals. The Boron ends up with no electrons in the outer shell, The complete inner shell is the same as group VIIIA helium. Low atomic weight elements (the first 20 elements) are most likely to adhere to the octet rule. Assign formal charges to atoms in the structure. Atoms follow the octet rule because they always seek the most stable electron configuration. this gives each of the florine ions eight electrons. Octet rule deals with the stability of an atom. The other halogen molecules (F 2, Br 2, I 2, and At 2) form bonds like those in the chlorine molecule: one single bond between atoms and three lone pairs of electrons per atom.This allows each halogen atom to have a noble gas electron configuration, which corresponds to eight valence electrons. Elements in and beyond the third period of the periodic table do not follow octet rule thus it applies … The octet rule is a chemical rule of thumb that reflects the observation that main group elements tend to bond in such a way that each atom has eight electrons in its valence shell, giving it the same electronic configuration as a noble gas.The rule is especially applicable to carbon, nitrogen, oxygen, and the halogens, but also to metals such as sodium or magnesium. According to this rule, an atom is stable if its outermost shell have total of 8 e –.It is a special case of the stability rule of atoms which suggests that the outermost shell should be completely filled for an atom to be stable. In P F 5 , S F 6 and H 2 S O 4 , the central atom has more than eight valence electrons hence they exhibit expanded octet. Why Elements Follow the Octet Rule . If they must obey the octet rule, then we do not obtain this linear strcutre::: O = :S = O :: ---> because the "S" atom has 10 electrons, disobeying the octet. Some structures don't obey the octet rule, but explain why. Simply we can see in the structure or SO2 that oxygen1 has 8 e in outermost shell as 2 it shares with S. Oxygen2 does not share instead is donated 2e by S i.e. Following the octet rule results in completely filled s- and p- orbitals in an atom's outermost energy level. Let us consider the electron dot structure of sulphuric acid, The chemical formula of Sulpuric acid is H 2 SO 4: NO , ICl_2^-1, XeF_4 BF_3 follows the octet rule because the Boron has three electrons so that it can give one electron to each of the three fluorine atoms. We can say that it follws extended form octet rule.