Final answer:
The chemist is using a chemical equation to represent the reaction of two elements, where the formulas of the reactants and products are written on the left and right sides of the equation, respectively, separated by a + sign.
Step-by-step explanation:
The chemist is using a chemical equation to represent the reaction of two elements. A chemical equation is a symbolic representation of a chemical reaction, where the formulas of the reactants are written on the left side of the equation, separated by a + sign, and the formulas of the products are written on the right side, also separated by a + sign. An arrow pointing in the direction of the products separates the reactants from the products.
For example, the reaction between methane (CH4) and oxygen (O2) to produce carbon dioxide (CO2) and water (H2O) can be represented by the chemical equation: CH4 + 2O2 → CO2 + 2H2O.