Exceptions in hybridisation of compounds?

Elements in groupsIA, IIA and IIIAdo not follow the "octet rule" that we used for the above problems. The electron-dot formula forBF₃is given as follows:

Someelements having low-energy d-orbitalsalso form exceptions to the "octet rule" in that more than eight electrons are accommodated around the central atom. The central atom in most of these compounds will be bonded to highly electronegative elements such as fluorine, oxygen and chlorine. A surprising element in this group is the inert gas, xenon. If xenon is exposed to fluorine gas in the presence of light for several weeks it can form XeF₂, a colorless crystalline solid.