A tetra-atomic molecule (P) on reaction with nitrogen (I) oxide, produces two substances (Q) and (R). (Q) is a dehydrating agent in its monomeric form while substance (R) is a diatomic gas which shows almost inert behaviour. The substances (P) and (Q) and (R) respectively will be (a) \(\mathrm{P}_{4}, \mathrm{~N}_{2} \mathrm{O}_{5}, \mathrm{~N}_{2}\) (b) \(\mathrm{P}_{4}, \mathrm{P}_{4} \mathrm{O}_{10}, \mathrm{~N}_{2}\) (c) \(\mathrm{P}_{4}, \mathrm{P}_{2} \mathrm{O}_{3}, \mathrm{H}_{2}\) (d) \(\mathrm{P}_{4}, \mathrm{P}_{2} \mathrm{O}_{3}, \mathrm{~N}_{2}\)

A tetra-atomic molecule is a compound that consists of just four atoms. This can pertain to molecules made up of four atoms of the same element or different elements. In our exercise, the tetra-atomic molecule in question is (P), which reacts with nitrogen oxide to produce two other substances.

Understanding the structure and properties of tetra-atomic molecules is crucial. For example, molecules like phosphorus (P₄) are tetra-atomic because they consist of four phosphorus atoms joined together. Such molecules often exhibit unique chemical and physical characteristics due to their specific atomic arrangement. The arrangement can influence reactivity, bonding, and other chemical behavior.

A dehydrating agent is a substance capable of removing water (H₂O) from another compound. These agents are used extensively in chemistry for various purposes including drying solvents, preserving biological specimens, and in the synthesis of anhydrous compounds.

In the context of our exercise, substance (Q) is a dehydrating agent in its monomeric form. Dehydrating agents, like phosphorus pentoxide (P₄O₁₀), are highly efficient at binding to water molecules and removing them from various environments. This process is often a physical or chemical change where the agent either absorbs the water or chemically reacts to bind with it, leaving behind a dried substance. Understanding the mechanism of action is important for its application in chemical reactions and industrial processes.

A diatomic inert gas is composed of molecules that contain two atoms and exhibit low chemical reactivity. In the natural world, inert or noble gases often come in diatomic forms under certain conditions. 'Inert' refers to the lack of chemical reactivity due to the full valence electron shell that these elements usually possess. This makes them stable and unreactive under typical circumstances.

In the exercise, substance (R) is a diatomic gas showing almost inert behaviour. Nitrogen (N₂) is an example of a diatomic gas that is relatively inert because of its strong triple bond holding the two nitrogen atoms together. Such gases are fundamental in chemical studies due to their non-reactive nature, and they are often used in environments where reactions need to be prevented or controlled.