ents to form oxides. O2 is required for us to breathe. Ozone, on the other hand, contains three atoms per molecule. Its formula is O3. Ozone is formed when oxygen in the air is subjected to an electrical discharge, such as a bolt of lightning. Ozone is considered a pollutant, because is attacks structural materials and the tissues of plants and animals. However, it does absorb a great deal of the ultraviolet radiation from the sun. It is also a colorless gas containing a strong, irritating odor. There is also O4, which contains four atoms per molecule. It is in a pale blue, nonmagnetic form, which can be easily broken down into ordinary oxygen. Oxygen combines with most elements, except the lower-atomic-weight noble gases, to form oxides. An oxide is a compound formed by the union of oxygen with another element. Hydrogen combines with oxygen to form hydrogen oxide, also known as ordinary water. Many oxides occur in nature. Water is the most common one. Carbon dioxide is also a common oxide in nature.When oxygen reacts with the metals of Groups I and II, high temperatures are required to start reactions with the lower-atomic-weight metals, such as lithium, sodium, potassium, magnesium, and calcium. The higher-atomic-weight metals, like rubidium, cesium, strontium, and barium, react spontaneously at room temperature. The electronegativity differences between oxygen and each of these metals is large. The oxygen compounds formed with them are ionic.When oxygen reacts with nonmetals, they usually occur at high temperatures of combustion, because the electronegativity differences between them are small. The oxides that result from them, contain covalent bonds and exist as molecules. When oxygen reacts with metals other than those of Groups I and II, they may occur slowly at room temperature. However, some may react rapidly if the temperature is raised.When oxygen and certain types of molds and bacteria are present, decay ...
