Nitric acid Nitric acid can oxidize non-active metals such as copper and silver. With these non-active or less electropositive metals the products depend on temperature and the acid concentration. For example, copper reacts with dilute nitric acid at ambient temperatures with a 3:8 stoichiometry: The nitric oxide produced may react with atmospheric oxygen to give nitrogen dioxide. With more concentrated nitric acid, nitrogen dioxide is produced directly in a reaction with 1:4 stoichiometry: Upon reaction with nitric acid, most metals give the corresponding nitrates. Some metalloids and metals give the oxides; for instance, Sn, As, Sb, and Ti are oxidized into SnO,
Acid–base reaction Instead of defining acid–base reactions in terms of protons or other bonded substances, the Lewis definition defines a base (referred to as a "Lewis base") to be a compound that can donate an "electron pair", and an acid (a "Lewis acid") to be a compound that can receive this electron pair. For example, boron trifluoride, BF is a typical Lewis acid. It can accept a pair of electrons as it has a vacancy in its octet. The fluoride ion has a full octet and can donate a pair of electrons. Thus is a typical Lewis acid, Lewis base reaction. All