It is believed that atoms combine with each other such that the outermost shell acquires a stable configuration of 8 electrons. If stability were attained with 6 electrons rather than 8; what would be the formula of the stable fluoride ion? (DUMET 2009)

In general, the stability of an atom will attain by sharing electrons to form an octet configuration (8 electrons) in the outermost shell. As the number of outermost electrons of fluorine is 7 2 2 5 1s 2s 2p it accepts one electron to form a fluorine anion F. If the stability is attainted by 6 electrons, fluorine loses one electron to form fluorine cation F.