oxygen
A B C D E F G H I J K L M N O P R S T U V W Z

O2, after nitrogen the most abundant gas in the atmosphere of the earth (20.95%). This element is found free as a colorless, tasteless odorless gas in the atmosphere. Molecular weight: 31.9988. It is active in physiological processes and produced by photosynthesis. The hydrosphere contains dissolved oxygen in about 1 % of the quantity present in the atmosphere.