4

# ${O}^{2-}$, ${F}^{F-}$, $N{a}^{+}$ and $M{g}^{2+}$ are isoelectronic, the order of increasing size is

${F}^{-}

${F}^{-}<{O}^{2-}

$M{g}^{++}<{F}^{-}

$M{g}^{++}

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