why the freedom of gas is restricted when it is adsorbed.?and why delta h becomes less and less negative during adsorption process

From dG = dH –  TdS

molecules looses degree of freedom.

but entropy of adsorption is negative,

enthalpy change is negative and the processis exothermic.

@ adyasha 
actually adsorption means the gas particle will be stick to the solid surface due to the uneven distribution of the particle in the solid state , and for that the solid surface will exert a force , and due to the low intermolecular attraction  between the particles of gas , they will not tend to remove from the surface and they will be remain attached their . 
due to that their freedom of movement will be restricted . 

and the process is exothermic due to liberation of heat when the gaseous particle will attach in the surface of solid adsorbate . 
HOPE IT CLEARS YOU 
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