Oxygen is a chemical element and its symbol is O. The atomic number of oxygen is 8 and its atomic mass is 16 amu(atomic mass unit). Oxygen belongs to the non-metals family. Oxygen is present in sixteenth group of periodic table. Oxygen is the second element of the sixteenth group. Therefore, the period number of oxygen is 2. The normal phase of oxygen is gas. The electronic configuration of oxygen is 1s2 2s2 2p4. Moreover, the number of electrons per shell of oxygen is 2 and 6.