If red spheres represent oxygen atoms, blue spheres represent nitrogen atoms, and all the molecules are gases, (7.4, 7.5) Reactants
→ Products
a. write the formula for each of the reactants and products.

Chemical symbols are shorthand representations of elements, where each element is denoted by one or two letters, such as 'O' for oxygen and 'N' for nitrogen. A chemical formula indicates the types and numbers of atoms in a molecule, such as O2 for diatomic oxygen or N2 for diatomic nitrogen. Understanding how to write these symbols and formulas is essential for accurately representing chemical substances.

Molecular structure refers to the arrangement of atoms within a molecule, including how they are bonded together. In the context of the question, the image shows different arrangements of red (oxygen) and blue (nitrogen) spheres, which represent the molecular structures of the reactants and products. Recognizing these structures helps in identifying the correct chemical formulas for the substances involved.

In a chemical reaction, reactants are the starting substances that undergo transformation, while products are the substances formed as a result of the reaction. The question involves identifying the reactants and products based on the molecular models provided. Understanding the distinction between these two categories is crucial for writing balanced chemical equations and formulas.