An exothermic reaction is a chemical reaction that produces a. bubbles of gas b. a new substance c. a precipitate d. heat energy

I pretty sure the answer is a

Atomicity occurs to prevent updates of the database occurring only partially, which can cause greater problems than rejecting the whole series outright.some are monatomic, diatomic, triatomic etc because it shows the number of atoms. for example, monatomic means it contains only one atom.