Give the oxidation number of the underlined atoms in the following molecules and ions: (a) $\mathrm {\underline{C l}}\mathrm{F}$, (b) $\underline{I}$$\mathrm{F}_{7}$, (c) $\underline{C}$$\mathrm{H}_{4}$,(d) $\underline{C}_{2}$$\mathrm{H}_{2}$,(e) $\underline{C}_{2}$$\mathrm{H}_{4}$,(f) $\mathrm{K}_{2}$$\underline{Cr}$$\mathrm{O}_{4}$,$(\mathrm{g}) \mathrm{K}_{2}$$\underline{Cr}_{2}$$\mathrm{O}_{7}$,(h) K$\underline{M n}$$\mathrm{O}_{4}$,(i) $\mathrm{NaH}$$\underline{C}$$\mathrm{O}_{3}$,(j) $\underline{L i}_{2}$,(k) $\mathrm{Na}$$\underline{I}$$\mathrm{O}_{3}$(1) $\mathrm{K}$$\underline{} \underline{0}_{2}$, $(\mathrm{m}) \underline{\mathrm{PF}}_{6}^{-}$,(n) $\mathrm{K}$$\underline{Au}$$\mathrm{Cl}_{4}$.