What is a chemical reaction

Anurse practitioner prepares an injection of promethazine, an antihistamine used to treat allergic rhinitis. if the stock bottle is labeled 25 mg/ml and the order is a dose of 11.0 mg , how many milliliters will the nurse draw up in the syringe?

An electrons position cannot be known precisely only it's probability of being in a certain location can be known

As changes in energy levels of electrons increase, the frequencies of atomic line spectra they emit