Final answer:
Clay is the inorganic material in soil with the smallest particle size, leading to the least amount of air and water space due to its ability to pack tightly together.
Step-by-step explanation:
The inorganic material found in soil that allows for the least amount of air and water space is clay. Soil contains various components including inorganic mineral matter, organic matter, water, and air. The inorganic portion consists of rock fragments that are broken down into different particle sizes such as sand, silt, and clay. Clay particles are the smallest, less than 0.002 mm in diameter, and thus they pack closely together, reducing porosity and permeability which in turn minimizes the space available for air and water. This can lead to soil compaction and may result in anoxic conditions harmful to plant life when the soil does not drain properly.