Oxygen as a chemical element
– Symbol: O
– Atomic number: 8
– Member of the chalcogen group in the periodic table
– Highly reactive nonmetal
– Forms oxides with most elements and compounds
Abundance and properties of oxygen
– Earth’s most abundant element after hydrogen and helium
– Constitutes 20.95% of the Earth’s atmosphere
– Colorless and odorless diatomic gas (O2)
– Pale blue in liquid and solid forms
– Standard atomic weight: 15.99903-15.99977 g/mol
Importance of oxygen in living organisms
– Essential for cellular respiration in plants, animals, and fungi
– Required for gas exchange in lungs and circulatory system
– Component of organic molecules (proteins, nucleic acids, etc.)
– Major constituent of water and living organisms
– Continuously replenished in Earth’s atmosphere by photosynthesis
Discovery and early experiments on oxygen
– Oxygen discovered independently by Michael Sendivogius, Carl Wilhelm Scheele, and Joseph Priestley
– Priestley called oxygen ‘dephlogisticated air’ and did not recognize it as a chemical element
– Name ‘oxygen’ coined by Antoine Lavoisier in 1777
– Relationship between combustion and air observed by Philo of Byzantium and Leonardo da Vinci
– Phlogiston theory prevalent before oxygen’s discovery
Common uses of oxygen
– Production of steel, plastics, textiles, and other materials
– Brazing, welding, and cutting of metals
– Rocket propellant in space exploration
– Oxygen therapy and life support systems in aircraft, submarines, and diving
– Important for various industrial and medical applications
