Following chromatogram was developed by adsorption of compound 'A' on a 6 cm TLC glass plate. Retardation factor of the compound 'A' is ______ $$\times 10^{-1}$$.

The retardation factor ((R_f)) in thin layer chromatography is defined as

$$R_f=\frac{\text{Distance travelled by the compound}}{\text{Distance travelled by the solvent front}}.$$

The compound travels a distance of

$$3.5\ \text{cm}.$$

The solvent front is (0.5\ \text{cm}) below the top edge of the plate, while the baseline is (0.5\ \text{cm}) above the bottom edge. Hence, the total distance travelled by the solvent front is

$$6-0.5-0.5=5.0\ \text{cm}.$$

Therefore,

$$R_f=\frac{3.5}{5.0}=0.7.$$

Expressing the value in the form (x\times10^{-1}),

$$0.7=7\times10^{-1}.$$

Hence,

$$\boxed{R_f=7\times10^{-1}},$$

so the required value is

$$\boxed{7}.$$