Why volume of a gas is negligible as compared to vessel?

The volume of a gas is considered negligible compared to that of its container because gas molecules are widely spaced apart and occupy a much larger volume than the individual molecules themselves. In a gas, the distance between molecules is significantly greater than their size, leading to a low density. This results in the gas having a volume that is primarily determined by the size of the vessel it occupies rather than the volume of the gas molecules themselves. Consequently, in ideal gas behavior, the actual volume of the gas particles is often ignored when calculating pressure and temperature relationships.