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ioic bonding
Generally ioic compounds contain metals and non metals. However the compound NH4Cl is ionic, and contains NH4+ and Cl- ,and all of the elements are non-metals.
In ioic compounds an electron is transferred forming the Ag+ ion.
Becasue the difference in electronegativity between S and O is only 0.86 which is insufficient for the formation of ioic bonds- the bonds are polar covalent with some pi bonding.
Beryllium is in the 2d period of the modern periodic table. Its electron config. is [He] 2s2 and forms the Be2+ ion by losing two elctrons and in this instance can be said to disobey the octet. In some compounds such as the hydride it also disobeys the octet rule. But in many others it does obey the octet rule! For example the difluoride, BeF2, is essentially covalent with four coordinate Be centers linked by flourine bridges.