Answer:
C. substances that are used up in a reaction
Explanation:
Substances are combined in a chemical reaction to give rise to other substances. The substances that come together are called REACTANTS while the substances that are produced are called PRODUCTS.
Reactants are used up in the reaction to give rise to new products at the end of the reaction. For example, in the reaction as follows:
6CO2 + 6H2O --> C6H12O6 + 6O2
CO2 (carbon dioxide) and water (H2O) are the REACTANTS of the reaction, which are used up to form glucose and oxygen (products)
Will you please tell about which model are you talking about? So, that I can help you because your seems to be incomplete.
Answer:

Explanation:
The second line in the Pfund series corresponds to a transition from n = 7 to n = 5.
To calculate the wavelength of the transition, we can use the Rydberg equation:

where

If n₁ = 5 and n₂ = 7

