Glosaurus
Chemical Elements

Oxygen

O 8

Essential for life and combustion processes.
Oxygen is a diatomic molecule consisting of two oxygen atoms, typically represented by the symbol O2. It is a colorless, odorless gas at room temperature and is essential for most forms of life on Earth, playing a crucial role in respiration and metabolism. Oxygen is also a highly reactive nonmetal and a member of the chalcogen group in the periodic table.
Symbol
O
Atomic number
8
Atomic mass
15.999
Classification
Nonmetals
Melting point
-218°C
Boiling point
-182°C
State of matter
Gas
Appearance
Colorless, odorless gas
Discovery and history
Oxygen was discovered in 1774 by the Swedish chemist Carl Wilhelm Scheele, who isolated it by heating mercuric oxide, though he did not publish his findings immediately. The element is most famously credited to the English scientist Joseph Priestley, who, in 1775, published his results of oxygen’s discovery after producing it from the heating of red mercuric oxide. However, it was Antoine Lavoisier, through his work in the late 18th century, who named it 'oxygen' from the Greek words meaning 'acid producer,' as he initially believed it was essential for the formation of acids. Lavoisier's work laid the foundation for modern chemistry, as he helped to discredit the phlogiston theory, which preceded our understanding of combustion and respiration. Throughout the 19th and 20th centuries, the importance of oxygen in supporting life and its chemical reactivity was further understood, leading to advances in various scientific fields, including biochemistry, medicine, and environmental science.
Natural occurrence
Oxygen is the most abundant element in the Earth's crust, composing approximately 46% of its weight. It occurs mainly in the form of oxides, such as silica (SiO2), which constitutes sand and various minerals. Additionally, oxygen is vital in water (H2O), where it combines with hydrogen. In the atmosphere, oxygen is present as about 21% of the total volume of Earth's air, formed primarily by the process of photosynthesis, where plants convert carbon dioxide and sunlight into organic matter while releasing oxygen as a byproduct. The oceans, which cover a significant portion of the Earth's surface, are also major reservoirs of oxygen, sustaining aquatic life through dissolved oxygen in the water. Overall, oxygen plays a pivotal role in both terrestrial and aquatic ecosystems.
Biological role and importance
Oxygen is critical for the survival of aerobic organisms, including humans, animals, and many microorganisms. During cellular respiration, oxygen is utilized to convert glucose into energy in the mitochondria, producing carbon dioxide and water as byproducts. This energy production is essential for various bodily functions, including muscle contraction, brain activity, and metabolic processes. In plants, oxygen is produced during photosynthesis, which not only serves as a vital energy source but also contributes to the oxygen content of the atmosphere. The presence of oxygen is crucial in environments where life exists, as it supports intricate biochemical pathways and the overall functioning of ecosystems. Additionally, oxygen is involved in various biochemical processes, including the synthesis of nucleotides and amino acids, making it indispensable for life.
Physical and chemical properties
Oxygen exists as a colorless, odorless gas at standard temperature and pressure (0 °C and 1 atmosphere). It has a boiling point of -183 °C and a melting point of -218 °C, making it a gas under normal conditions. As a diatomic molecule (O2), it has a density of 1.429 kg/m³, making it lighter than air. Oxygen is highly reactive and can form compounds with nearly all other elements, often in the form of oxides. It supports combustion and is a strong oxidizing agent, readily reacting with a variety of substances. For example, it reacts with metals to form metal oxides and can result in rapid oxidation processes, such as combustion. Other allotropes of oxygen include ozone (O3), which is a pale blue gas found in the Earth's stratosphere, where it forms a protective layer absorbing harmful ultraviolet radiation from the sun.
Uses and applications
Oxygen has numerous practical applications across various fields. In medicine, it is crucial for patient care, especially in respiratory treatments, where supplemental oxygen is administered to individuals with breathing difficulties or during surgical procedures. Oxygen is also essential in industrial processes, particularly in the production of steel, where it is used to facilitate combustion in furnaces. Moreover, it is used in water treatment facilities to promote microbial activity, aiding in the breakdown of organic matter. In aerospace, liquid oxygen serves as a propellant component for rockets. Additionally, oxygen is widely employed in welding and cutting metals, and in the production of various chemicals such as acids and pharmaceuticals. The importance of oxygen extends to environmental applications, where it is utilized in waste management and bioremediation processes.
Did you know?
  • Oxygen was the first element to be discovered that was essential for life.
  • While we breathe in oxygen, most of it comes from oceanic phytoplankton, not terrestrial plants.
  • Liquid oxygen is pale blue in color and can be extremely cold; it can cause severe frostbite upon direct contact with skin.
  • Ozone (O3), an allotrope of oxygen, is beneficial in the stratosphere but harmful at ground level due to its reactive nature.
  • Oxygen can exist in a gaseous form as well as be dissolved in water, which is important for aquatic life.